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<html lang="en">
<head>
<title>GHDL guide</title>
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<h1 class="settitle">GHDL guide</h1>
<div class="contents">
<h2>Table of Contents</h2>
<ul>
<li><a name="toc_Top" href="#Top">GHDL guide</a>
<li><a name="toc_Introduction" href="#Introduction">1 Introduction</a>
<ul>
<li><a href="#Introduction">1.1 Content of this manual</a>
<li><a href="#What-is-VHDL">1.2 What is <code>VHDL</code>?</a>
<li><a href="#What-is-GHDL">1.3 What is <code>GHDL</code>?</a>
</li></ul>
<li><a name="toc_Starting-with-GHDL" href="#Starting-with-GHDL">2 Starting with GHDL</a>
<ul>
<li><a href="#The-hello-word-program">2.1 The hello world program</a>
<li><a href="#A-full-adder">2.2 A full adder</a>
<li><a href="#Starting-with-a-design">2.3 Starting with a design</a>
</li></ul>
<li><a name="toc_Invoking-GHDL" href="#Invoking-GHDL">3 Invoking GHDL</a>
<ul>
<li><a href="#Building-commands">3.1 Building commands</a>
<ul>
<li><a href="#Analysis-command">3.1.1 Analysis command</a>
<li><a href="#Elaboration-command">3.1.2 Elaboration command</a>
<li><a href="#Run-command">3.1.3 Run command</a>
<li><a href="#Elaborate-and-run-command">3.1.4 Elaborate and run command</a>
<li><a href="#Bind-command">3.1.5 Bind command</a>
<li><a href="#Link-command">3.1.6 Link command</a>
<li><a href="#List-link-command">3.1.7 List link command</a>
<li><a href="#Check-syntax-command">3.1.8 Check syntax command</a>
<li><a href="#Analyze-and-elaborate-command">3.1.9 Analyze and elaborate command</a>
</li></ul>
<li><a href="#GHDL-options">3.2 GHDL options</a>
<li><a href="#Passing-options-to-other-programs">3.3 Passing options to other programs</a>
<li><a href="#GHDL-warnings">3.4 GHDL warnings</a>
<li><a href="#Rebuilding-commands">3.5 Rebuilding commands</a>
<ul>
<li><a href="#Import-command">3.5.1 Import command</a>
<li><a href="#Make-command">3.5.2 Make command</a>
<li><a href="#Generate-Makefile-command">3.5.3 Generate Makefile command</a>
</li></ul>
<li><a href="#Library-commands">3.6 Library commands</a>
<ul>
<li><a href="#Directory-command">3.6.1 Directory command</a>
<li><a href="#Clean-command">3.6.2 Clean command</a>
<li><a href="#Remove-command">3.6.3 Remove command</a>
<li><a href="#Copy-command">3.6.4 Copy command</a>
</li></ul>
<li><a href="#Cross_002dreference-command">3.7 Cross-reference command</a>
<li><a href="#File-commands">3.8 File commands</a>
<ul>
<li><a href="#Pretty-print-command">3.8.1 Pretty print command</a>
<li><a href="#Find-command">3.8.2 Find command</a>
<li><a href="#Chop-command">3.8.3 Chop command</a>
<li><a href="#Lines-command">3.8.4 Lines command</a>
</li></ul>
<li><a href="#Misc-commands">3.9 Misc commands</a>
<ul>
<li><a href="#Help-command">3.9.1 Help command</a>
<li><a href="#Dispconfig-command">3.9.2 Dispconfig command</a>
<li><a href="#Disp-standard-command">3.9.3 Disp standard command</a>
<li><a href="#Version-command">3.9.4 Version command</a>
</li></ul>
<li><a href="#Installation-Directory">3.10 Installation Directory</a>
<li><a href="#IEEE-library-pitfalls">3.11 IEEE library pitfalls</a>
<li><a href="#IEEE-math-packages">3.12 IEEE math packages</a>
</li></ul>
<li><a name="toc_Simulation-and-runtime" href="#Simulation-and-runtime">4 Simulation and runtime</a>
<ul>
<li><a href="#Simulation-options">4.1 Simulation options</a>
<li><a href="#Debugging-VHDL-programs">4.2 Debugging VHDL programs</a>
</li></ul>
<li><a name="toc_GHDL-implementation-of-VHDL" href="#GHDL-implementation-of-VHDL">5 GHDL implementation of VHDL</a>
<ul>
<li><a href="#VHDL-standards">5.1 VHDL standards</a>
<li><a href="#Source-representation">5.2 Source representation</a>
<li><a href="#Library-database">5.3 Library database</a>
<li><a href="#VHDL-files-format">5.4 VHDL files format</a>
<li><a href="#Top-entity">5.5 Top entity</a>
<li><a href="#Using-vendor-libraries">5.6 Using vendor libraries</a>
<li><a href="#Using-ieee_002emath_005freal-or-ieee_002emath_005fcomplex">5.7 Using ieee.math_real or ieee.math_complex</a>
<li><a href="#Interfacing-to-other-languages">5.8 Interfacing to other languages</a>
<ul>
<li><a href="#Interfacing-to-other-languages">5.8.1 Foreign declarations</a>
<li><a href="#Restrictions-on-foreign-declarations">5.8.2 Restrictions on foreign declarations</a>
<li><a href="#Linking-with-foreign-object-files">5.8.3 Linking with foreign object files</a>
<li><a href="#Starting-a-simulation-from-a-foreign-program">5.8.4 Starting a simulation from a foreign program</a>
<li><a href="#Linking-with-Ada">5.8.5 Linking with Ada</a>
<li><a href="#Using-GRT-from-Ada">5.8.6 Using GRT from Ada</a>
</li></ul>
</li></ul>
<li><a name="toc_GHDL-implementation-of-VITAL" href="#GHDL-implementation-of-VITAL">6 GHDL implementation of VITAL</a>
<ul>
<li><a href="#VITAL-packages">6.1 VITAL packages</a>
<li><a href="#VHDL-restrictions-for-VITAL">6.2 VHDL restrictions for VITAL</a>
<li><a href="#Backannotation">6.3 Backannotation</a>
<li><a href="#Negative-constraint-calculation">6.4 Negative constraint calculation</a>
</li></ul>
<li><a name="toc_Flaws-and-bugs-report" href="#Flaws-and-bugs-report">7 Flaws and bugs report</a>
<ul>
<li><a href="#Deficiencies">7.1 Deficiencies</a>
<li><a href="#Reporting-bugs">7.2 Reporting bugs</a>
<li><a href="#Future-improvements">7.3 Future improvements</a>
</li></ul>
<li><a name="toc_Copyrights" href="#Copyrights">8 Copyrights</a>
<li><a name="toc_Index" href="#Index">Index</a>
</li></ul>
</div>



<div class="node">
<p><hr>
<a name="Top"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Introduction">Introduction</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#dir">(dir)</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#dir">(dir)</a>

</div>

<h2 class="unnumbered">GHDL guide</h2>

<p>GHDL, a VHDL compiler.

   <p>Copyright &copy; 2002, 2003, 2004, 2005, 2006, 2007 Tristan Gingold.

   <p>Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation.

<ul class="menu">
<li><a accesskey="1" href="#Introduction">Introduction</a>:                 What is GHDL, what is VHDL
<li><a accesskey="2" href="#Starting-with-GHDL">Starting with GHDL</a>:           Build a VHDL program with GHDL
<li><a accesskey="3" href="#Invoking-GHDL">Invoking GHDL</a>
<li><a accesskey="4" href="#Simulation-and-runtime">Simulation and runtime</a>
<li><a accesskey="5" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>
<li><a accesskey="6" href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a>
<li><a accesskey="7" href="#Flaws-and-bugs-report">Flaws and bugs report</a>
<li><a accesskey="8" href="#Copyrights">Copyrights</a>
<li><a accesskey="9" href="#Index">Index</a>
</ul>

<div class="node">
<p><hr>
<a name="Introduction"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Starting-with-GHDL">Starting with GHDL</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Top">Top</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h2 class="chapter">1 Introduction</h2>

<ul class="menu">
<li><a accesskey="1" href="#What-is-VHDL">What is VHDL</a>
<li><a accesskey="2" href="#What-is-GHDL">What is GHDL</a>
</ul>

<h3 class="section">1.1 Content of this manual</h3>

<p>This manual is the user and reference manual for GHDL.  It does not
contain an introduction to VHDL.  Thus, the reader should have at least
a basic knowledge of VHDL.  A good knowledge of VHDL language reference
manual (usually called LRM) is a plus.

<!-- FIXME: references: URL, LRM reference. -->
<div class="node">
<p><hr>
<a name="What-is-VHDL"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#What-is-GHDL">What is GHDL</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Introduction">Introduction</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Introduction">Introduction</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">1.2 What is <code>VHDL</code>?</h3>

<p><dfn>VHDL</dfn> is an acronym for Very High Speed Integrated Circuit Hardware
Description Language which is a programming language used to describe a
logic circuit by function, data flow behaviour, or structure.

   <p><code>VHDL</code> <em>is</em> a programming language: although <code>VHDL</code> was
not designed for writing general purpose programs, you can write any
algorithm with the <code>VHDL</code> language.  If you are able to write
programs, you will find in <code>VHDL</code> features similar to those found
in procedural languages such as <code>C</code>, <code>Pascal</code> or <code>Ada</code>. 
<code>VHDL</code> derives most of its syntax and semantics from <code>Ada</code>. 
Knowing <code>Ada</code> is an advantage for learning <code>VHDL</code> (it is an
advantage in general as well).

   <p>However, <code>VHDL</code> was not designed as a general purpose language but as an
<code>HDL</code> (hardware description language).  As the name implies, <code>VHDL</code>
aims at modeling or documenting electronics systems.  Due to the nature
of hardware components which are always running, <code>VHDL</code> is a highly
concurrent language, built upon an event-based timing model.

   <p>Like a program written in any other language, a <code>VHDL</code> program
can be executed. Since <code>VHDL</code> is used to model designs, the term
<dfn>simulation</dfn> is often used instead of <dfn>execution</dfn>, with the
same meaning.

   <p>Like a program written in another hardware description language, a
<code>VHDL</code> program can be transformed with a <code>synthesis tool</code>
into a netlist, that is, a detailed gate-level implementation.

<div class="node">
<p><hr>
<a name="What-is-GHDL"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#What-is-VHDL">What is VHDL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Introduction">Introduction</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">1.3 What is <code>GHDL</code>?</h3>

<p><dfn>GHDL</dfn> is a shorthand for G Hardware Design Language.  Currently,
<code>G</code> has no meaning.

   <p><dfn>GHDL</dfn> is a <code>VHDL</code> compiler that can execute (nearly) any
<code>VHDL</code> program. <code>GHDL</code> is <em>not</em> a synthesis tool: you cannot
create a netlist with <code>GHDL</code>.

   <p>Unlike some other simulators, <code>GHDL</code> is a compiler: it directly
translates a <code>VHDL</code> file to machine code, using the <code>GCC</code>
back-end and without using an intermediary language such as <code>C</code>
or <code>C++</code>.  Therefore, the compiled code should be faster and
the analysis time should be shorter than with a compiler using an
intermediary language.

   <p>The Windows(TM) version of <code>GHDL</code> is not based on <code>GCC</code> but on
an internal code generator.

   <p>The current version of <code>GHDL</code> does not contain any graphical
viewer: you cannot see signal waves.  You can still check with a test
bench.  The current version can produce a <code>VCD</code> file which can be
viewed with a wave viewer, as well as <code>ghw</code> files to be viewed by
&lsquo;<samp><span class="samp">gtkwave</span></samp>&rsquo;.

   <p><code>GHDL</code> aims at implementing <code>VHDL</code> as defined by IEEE 1076. 
It supports most of the 1987 standard and most features added by the
1993 standard.

<div class="node">
<p><hr>
<a name="Starting-with-GHDL"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Invoking-GHDL">Invoking GHDL</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Introduction">Introduction</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h2 class="chapter">2 Starting with GHDL</h2>

<p>In this chapter, you will learn how to use the GHDL compiler by
working on two examples.

<ul class="menu">
<li><a accesskey="1" href="#The-hello-word-program">The hello word program</a>
<li><a accesskey="2" href="#A-full-adder">A full adder</a>
<li><a accesskey="3" href="#Starting-with-a-design">Starting with a design</a>
</ul>

<div class="node">
<p><hr>
<a name="The-hello-word-program"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#A-full-adder">A full adder</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Starting-with-GHDL">Starting with GHDL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Starting-with-GHDL">Starting with GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">2.1 The hello world program</h3>

<p>To illustrate the large purpose of VHDL, here is a commented VHDL
"Hello world" program.

<pre class="example">     --  <span class="roman">Hello world program.</span>
     use std.textio.all; --  <span class="roman">Imports the standard textio package.</span>
     
     --  <span class="roman">Defines a design entity, without any ports.</span>
     entity hello_world is
     end hello_world;
     
     architecture behaviour of hello_world is
     begin
        process
           variable l : line;
        begin
           write (l, String'("Hello world!"));
           writeline (output, l);
           wait;
        end process;
     end behaviour;
</pre>
   <p>Suppose this program is contained in the file <samp><span class="file">hello.vhdl</span></samp>. 
First, you have to compile the file; this is called <dfn>analysis</dfn> of a design
file in VHDL terms.
<pre class="smallexample">     $ ghdl -a hello.vhdl
</pre>
   <p>This command creates or updates a file <samp><span class="file">work-obj93.cf</span></samp>, which
describes the library &lsquo;<samp><span class="samp">work</span></samp>&rsquo;.  On GNU/Linux, this command generates a
file <samp><span class="file">hello.o</span></samp>, which is the object file corresponding to your
VHDL program.  The object file is not created on Windows.

   <p>Then, you have to build an executable file.
<pre class="smallexample">     $ ghdl -e hello_world
</pre>
   <p>The &lsquo;<samp><span class="samp">-e</span></samp>&rsquo; option means <dfn>elaborate</dfn>.  With this option, <code>GHDL</code>
creates code in order to elaborate a design, with the &lsquo;<samp><span class="samp">hello</span></samp>&rsquo;
entity at the top of the hierarchy.

   <p>On GNU/Linux, the result is an executable program called <samp><span class="file">hello</span></samp>
which can be run:
<pre class="smallexample">     $ ghdl -r hello_world
</pre>
   <p>or directly:
<pre class="smallexample">     $ ./hello_world
</pre>
   <p>On Windows, no file is created.  The simulation is launched using this command:
<pre class="smallexample">     &gt; ghdl -r hello_world
</pre>
   <p>The result of the simulation appears on the screen:
<pre class="smallexample">     Hello world!
</pre>
   <div class="node">
<p><hr>
<a name="A-full-adder"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Starting-with-a-design">Starting with a design</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#The-hello-word-program">The hello word program</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Starting-with-GHDL">Starting with GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">2.2 A full adder</h3>

<p>VHDL is generally used for hardware design.  This example starts with
a full adder described in the <samp><span class="file">adder.vhdl</span></samp> file:

<pre class="example">     entity adder is
       -- <var>i0</var><span class="roman">, </span><var>i1</var><span class="roman"> and the carry-in </span><var>ci</var><span class="roman"> are inputs of the adder.</span>
       -- <var>s</var><span class="roman"> is the sum output, </span><var>co</var><span class="roman"> is the carry-out.</span>
       port (i0, i1 : in bit; ci : in bit; s : out bit; co : out bit);
     end adder;
     
     architecture rtl of adder is
     begin
        --  <span class="roman">This full-adder architecture contains two concurrent assignment.</span>
        --  <span class="roman">Compute the sum.</span>
        s &lt;= i0 xor i1 xor ci;
        --  <span class="roman">Compute the carry.</span>
        co &lt;= (i0 and i1) or (i0 and ci) or (i1 and ci);
     end rtl;
</pre>
   <p>You can analyze this design file:
<pre class="smallexample">     $ ghdl -a adder.vhdl
</pre>
   <p>You can try to execute the &lsquo;<samp><span class="samp">adder</span></samp>&rsquo; design, but this is useless,
since nothing externally visible will happen.  In order to
check this full adder, a testbench has to be run.  This testbench is
very simple, since the adder is also simple: it checks exhaustively all
inputs.  Note that only the behaviour is tested, timing constraints are
not checked.  The file <samp><span class="file">adder_tb.vhdl</span></samp> contains the testbench for
the adder:
<pre class="example">     --  <span class="roman">A testbench has no ports.</span>
     entity adder_tb is
     end adder_tb;
     
     architecture behav of adder_tb is
        --  <span class="roman">Declaration of the component that will be instantiated.</span>
        component adder
          port (i0, i1 : in bit; ci : in bit; s : out bit; co : out bit);
        end component;
        --  <span class="roman">Specifies which entity is bound with the component.</span>
        for adder_0: adder use entity work.adder;
        signal i0, i1, ci, s, co : bit;
     begin
        --  <span class="roman">Component instantiation.</span>
        adder_0: adder port map (i0 =&gt; i0, i1 =&gt; i1, ci =&gt; ci,
                                 s =&gt; s, co =&gt; co);
     
        --  <span class="roman">This process does the real job.</span>
        process
           type pattern_type is record
              --  <span class="roman">The inputs of the adder.</span>
              i0, i1, ci : bit;
              --  <span class="roman">The expected outputs of the adder.</span>
              s, co : bit;
           end record;
           --  <span class="roman">The patterns to apply.</span>
           type pattern_array is array (natural range &lt;&gt;) of pattern_type;
           constant patterns : pattern_array :=
             (('0', '0', '0', '0', '0'),
              ('0', '0', '1', '1', '0'),
              ('0', '1', '0', '1', '0'),
              ('0', '1', '1', '0', '1'),
              ('1', '0', '0', '1', '0'),
              ('1', '0', '1', '0', '1'),
              ('1', '1', '0', '0', '1'),
              ('1', '1', '1', '1', '1'));
        begin
           --  <span class="roman">Check each pattern.</span>
           for i in patterns'range loop
              --  <span class="roman">Set the inputs.</span>
              i0 &lt;= patterns(i).i0;
              i1 &lt;= patterns(i).i1;
              ci &lt;= patterns(i).ci;
              --  <span class="roman">Wait for the results.</span>
              wait for 1 ns;
              --  <span class="roman">Check the outputs.</span>
              assert s = patterns(i).s
                 report "bad sum value" severity error;
              assert co = patterns(i).co
                 report "bad carray out value" severity error;
           end loop;
           assert false report "end of test" severity note;
           --  <span class="roman">Wait forever; this will finish the simulation.</span>
           wait;
        end process;
     end behav;
</pre>
   <p>As usual, you should analyze the design:
<pre class="smallexample">     $ ghdl -a adder_tb.vhdl
</pre>
   <p>And build an executable for the testbench:
<pre class="smallexample">     $ ghdl -e adder_tb
</pre>
   <p>You do not need to specify which object files are required: GHDL knows them
and automatically adds them in the executable.  Now, it is time to run the
testbench:
<pre class="smallexample">     $ ghdl -r adder_tb
     adder_tb.vhdl:52:7:(assertion note): end of test
</pre>
   <p>If your design is rather complex, you'd like to inspect signals.  Signals
value can be dumped using the VCD file format.  The resulting file can be
read with a wave viewer such as GTKWave.  First, you should simulate your
design and dump a waveform file:
<pre class="smallexample">     $ ghdl -r adder_tb --vcd=adder.vcd
</pre>
   <p>Then, you may now view the waves:
<pre class="smallexample">     $ gtkwave adder.vcd
</pre>
   <p>See <a href="#Simulation-options">Simulation options</a>, for more details on the <samp><span class="option">--vcd</span></samp> option and
other runtime options.

<div class="node">
<p><hr>
<a name="Starting-with-a-design"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#A-full-adder">A full adder</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Starting-with-GHDL">Starting with GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">2.3 Starting with a design</h3>

<p>Unless you are only studying VHDL, you will work with bigger designs than
the ones of the previous examples.

   <p>Let's see how to analyze and run a bigger design, such as the DLX model
suite written by Peter Ashenden which is distributed under the terms of the
GNU General Public License.  A copy is kept on
&lt;<code>http://ghdl.free.fr/dlx.tar.gz</code>&gt;

   <p>First, untar the sources:
<pre class="smallexample">     $ tar zxvf dlx.tar.gz
</pre>
   <p>In order not to pollute the sources with the library, it is a good idea
to create a <samp><span class="file">work/</span></samp> subdirectory for the &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo; library.  To
any GHDL commands, we will add the <samp><span class="option">--workdir=work</span></samp> option, so
that all files generated by the compiler (except the executable) will be
placed in this directory.
<pre class="smallexample">     $ cd dlx
     $ mkdir work
</pre>
   <p>We will run the &lsquo;<samp><span class="samp">dlx_test_behaviour</span></samp>&rsquo; design.  We need to analyze
all the design units for the design hierarchy, in the correct order. 
GHDL provides an easy way to do this, by importing the sources:
<pre class="smallexample">     $ ghdl -i --workdir=work *.vhdl
</pre>
   <p>and making a design:
<pre class="smallexample">     $ ghdl -m --workdir=work dlx_test_behaviour
</pre>
   <p>Before this second stage, GHDL knows all the design units of the DLX,
but no one have been analyzed.  The make command of GHDL analyzes and
elaborates a design.  This creates many files in the <samp><span class="file">work/</span></samp>
directory, and the <samp><span class="file">dlx_test_behaviour</span></samp> executable in the current
directory.

   <p>The simulation needs to have a DLX program contained in the file
<samp><span class="file">dlx.out</span></samp>.  This memory image will be be loaded in the DLX memory. 
Just take one sample:
<pre class="smallexample">     $ cp test_loop.out dlx.out
</pre>
   <p>And you can run the test suite:
<pre class="smallexample">     $ ghdl -r dlx_test_behaviour
</pre>
   <p>The test bench monitors the bus and displays each instruction executed. 
It finishes with an assertion of severity level note:
<pre class="smallexample">     dlx-behaviour.vhdl:395:11:(assertion note): TRAP instruction
      encountered, execution halted
</pre>
   <p>Since the clock is still running, you have to manually stop the program
with the <kbd>C-c</kbd> key sequence.  This behavior prevents you from running the
test bench in batch mode.  However, you may force the simulator to
stop when an assertion above or equal a certain severity level occurs:
<pre class="smallexample">     $ ghdl -r dlx_test_behaviour --assert-level=note
</pre>
   <p>With this option, the program stops just after the previous message:
<pre class="smallexample">     dlx-behaviour.vhdl:395:11:(assertion note): TRAP instruction
      encountered, execution halted
     error: assertion failed
</pre>
   <p>If you want to make room on your hard drive, you can either:
     <ul>
<li>clean the design library with the GHDL command:
     <pre class="smallexample">          $ ghdl --clean --workdir=work
</pre>
     <p>This removes the executable and all the object files.  If you want to
rebuild the design at this point, just do the make command as shown above. 
<li>remove the design library with the GHDL command:
     <pre class="smallexample">          $ ghdl --remove --workdir=work
</pre>
     <p>This removes the executable, all the object files and the library file. 
If you want to rebuild the design, you have to import the sources again,
and to make the design. 
<li>remove the <samp><span class="file">work/</span></samp> directory:
     <pre class="smallexample">          $ rm -rf work
</pre>
     <p>Only the executable is kept.  If you want to rebuild the design, create
the <samp><span class="file">work/</span></samp> directory, import the sources, and make the design. 
</ul>

   <p>Sometimes, a design does not fully follow the VHDL standards.  For example it
uses the badly engineered &lsquo;<samp><span class="samp">std_logic_unsigned</span></samp>&rsquo; package.  GHDL supports
this VHDL dialect through some options:
<pre class="smallexample">     --ieee=synopsys -fexplicit
</pre>
   <p>See <a href="#IEEE-library-pitfalls">IEEE library pitfalls</a>, for more details.

<div class="node">
<p><hr>
<a name="Invoking-GHDL"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Simulation-and-runtime">Simulation and runtime</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Starting-with-GHDL">Starting with GHDL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h2 class="chapter">3 Invoking GHDL</h2>

<p>The form of the <code>ghdl</code> command is

<pre class="smallexample">     $ ghdl <var>command</var> [<var>options<small class="dots">...</small></var>]
</pre>
   <p>The GHDL program has several commands.  The first argument selects
the commands.  The options are used to slightly modify the action.

   <p>No options are allowed before the command.  Except for the run commands,
no options are allowed after a filename or a unit name.

<ul class="menu">
<li><a accesskey="1" href="#Building-commands">Building commands</a>
<li><a accesskey="2" href="#GHDL-options">GHDL options</a>
<li><a accesskey="3" href="#Passing-options-to-other-programs">Passing options to other programs</a>
<li><a accesskey="4" href="#GHDL-warnings">GHDL warnings</a>
<li><a accesskey="5" href="#Rebuilding-commands">Rebuilding commands</a>
<li><a accesskey="6" href="#Library-commands">Library commands</a>
<li><a accesskey="7" href="#Cross_002dreference-command">Cross-reference command</a>
<li><a accesskey="8" href="#File-commands">File commands</a>
<li><a accesskey="9" href="#Misc-commands">Misc commands</a>
<li><a href="#Installation-Directory">Installation Directory</a>
<li><a href="#IEEE-library-pitfalls">IEEE library pitfalls</a>
<li><a href="#IEEE-math-packages">IEEE math packages</a>
</ul>

<div class="node">
<p><hr>
<a name="Building-commands"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#GHDL-options">GHDL options</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Invoking-GHDL">Invoking GHDL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.1 Building commands</h3>

<p>The mostly used commands of GHDL are those to analyze and elaborate a design.

<ul class="menu">
<li><a accesskey="1" href="#Analysis-command">Analysis command</a>
<li><a accesskey="2" href="#Elaboration-command">Elaboration command</a>
<li><a accesskey="3" href="#Run-command">Run command</a>
<li><a accesskey="4" href="#Elaborate-and-run-command">Elaborate and run command</a>
<li><a accesskey="5" href="#Bind-command">Bind command</a>
<li><a accesskey="6" href="#Link-command">Link command</a>
<li><a accesskey="7" href="#List-link-command">List link command</a>
<li><a accesskey="8" href="#Check-syntax-command">Check syntax command</a>
<li><a accesskey="9" href="#Analyze-and-elaborate-command">Analyze and elaborate command</a>
</ul>

<div class="node">
<p><hr>
<a name="Analysis-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Elaboration-command">Elaboration command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Building-commands">Building commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.1.1 Analysis command</h4>

<p><a name="index-analysis-1"></a><a name="index-g_t_0040option_007b_002da_007d-command-2"></a>
<pre class="smallexample">     $ ghdl -a [<var>options</var>] <var>files</var>
</pre>
   <p>The <dfn>analysis</dfn> command compiles one or more files, and creates an
object file for each source file.  The analysis command is selected with
<var>-a</var> switch.  Any argument starting with a dash is an option, the
others are filenames.  No options are allowed after a filename
argument. GHDL analyzes each filename in the given order, and stops the
analysis in case of error (the following files are not analyzed). 
<!-- FIXME: check this. -->

   <p>See <a href="#GHDL-options">GHDL options</a>, for details on the GHDL options.  For example,
to produce debugging information such as line numbers, use:

<pre class="smallexample">     $ ghdl -a -g my_design.vhdl
</pre>
   <div class="node">
<p><hr>
<a name="Elaboration-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Run-command">Run command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Analysis-command">Analysis command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.1.2 Elaboration command</h4>

<p><a name="index-elaboration-3"></a><a name="index-g_t_0040option_007b_002de_007d-command-4"></a>
<pre class="smallexample">     $ ghdl -e [<var>options</var>] <var>primary_unit</var> [<var>secondary_unit</var>]
</pre>
   <p>On GNU/Linux the <dfn>elaboration</dfn> command creates an executable
containing the code of the <code>VHDL</code> sources, the elaboration code
and simulation code to execute a design hierarchy. On Windows this
command elaborates the design but does not generate anything.

   <p>The elaboration command is selected with <var>-e</var> switch, and must be
followed by either:

     <ul>
<li>a name of a configuration unit
<li>a name of an entity unit
<li>a name of an entity unit followed by a name of an architecture unit
</ul>

   <p>Name of the units must be a simple name, without any dot.  You can
select the name of the &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo; library with the <samp><span class="option">--work=NAME</span></samp>
option, as described in <a href="#GHDL-options">GHDL options</a>.

   <p>See <a href="#Top-entity">Top entity</a>, for the restrictions on the root design of a
hierarchy.

   <p>On GNU/Linux the filename of the executable is the name of the
primary unit, or for the later case, the concatenation of the name of
the primary unit, a dash, and the name of the secondary unit (or
architecture).  On Windows there is no executable generated.

   <p>The <samp><span class="option">-o</span></samp> followed by a filename can override the default
executable filename.

   <p>For the elaboration command, <code>GHDL</code> re-analyzes all the
configurations, entities, architectures and package declarations, and
creates the default configurations and the default binding indications
according to the LRM rules.  It also generates the list of objects files
required for the executable.  Then, it links all these files with the
runtime library.

   <p>The actual elaboration is performed at runtime.

   <p>On Windows this command can be skipped because it is also done by the
run command.

<div class="node">
<p><hr>
<a name="Run-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Elaborate-and-run-command">Elaborate and run command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Elaboration-command">Elaboration command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.1.3 Run command</h4>

<p><a name="index-run-5"></a><a name="index-g_t_0040option_007b_002dr_007d-command-6"></a>Run (or simulate) a design.

<pre class="smallexample">     $ ghdl -r [<var>options</var>] <var>primary_unit</var> [<var>secondary_unit</var>] [<var>simulation_options</var>]
</pre>
   <p>The options and arguments are the same as for the elaboration command, see <a href="#Elaboration-command">Elaboration command</a>.

   <p>On GNU/Linux this command simply determines the filename of the executable
and executes it.  Options are ignored. You may also directly execute
the program.

   <p>This command exists for three reasons:
     <ul>
<li>You don't have to create the executable program name. 
<li>It is coherent with the &lsquo;<samp><span class="samp">-a</span></samp>&rsquo; and &lsquo;<samp><span class="samp">-e</span></samp>&rsquo; commands. 
<li>It works with the Windows implementation, where the code is generated in
memory. 
</ul>

   <p>On Windows this command elaborates and launches the simulation.  As a consequence
you must use the same options used during analysis.

   <p>See <a href="#Simulation-and-runtime">Simulation and runtime</a>, for details on options.

<div class="node">
<p><hr>
<a name="Elaborate-and-run-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Bind-command">Bind command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Run-command">Run command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.1.4 Elaborate and run command</h4>

<p><a name="index-elaborate-and-run-7"></a><a name="index-g_t_0040option_007b_002d_002delab_002drun_007d-command-8"></a>Elaborate and then simulate a design unit.

<pre class="smallexample">     $ ghdl --elab-run [<var>elab_options</var>] <var>primary_unit</var> [<var>secondary_unit</var>] [<var>run_options</var>]
</pre>
   <p>This command acts like the elaboration command (see <a href="#Elaboration-command">Elaboration command</a>)
followed by the run command (see <a href="#Run-command">Run command</a>).

<div class="node">
<p><hr>
<a name="Bind-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Link-command">Link command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Elaborate-and-run-command">Elaborate and run command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<h4 class="subsection">3.1.5 Bind command</h4>

<p><a name="index-binding-9"></a><a name="index-g_t_0040option_007b_002d_002dbind_007d-command-10"></a>Bind a design unit and prepare the link step.

<pre class="smallexample">     $ ghdl --bind [<var>options</var>] <var>primary_unit</var> [<var>secondary_unit</var>]
</pre>
   <p>This command is only available on GNU/Linux.

   <p>This performs only the first stage of the elaboration command; the list
of objects files is created but the executable is not built.  This
command should be used only when the main entry point is not ghdl.

<div class="node">
<p><hr>
<a name="Link-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#List-link-command">List link command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Bind-command">Bind command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<h4 class="subsection">3.1.6 Link command</h4>

<p><a name="index-linking-11"></a><a name="index-g_t_0040option_007b_002d_002dlink_007d-command-12"></a>Link an already bound design unit.

<pre class="smallexample">     $ ghdl --link [<var>options</var>] <var>primary_unit</var> [<var>secondary_unit</var>]
</pre>
   <p>This performs only the second stage of the elaboration command: the
executable is created by linking the files of the object files list. 
This command is available only for completeness.  The elaboration command is
equivalent to the bind command followed by the link command.

<div class="node">
<p><hr>
<a name="List-link-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Check-syntax-command">Check syntax command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Link-command">Link command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<h4 class="subsection">3.1.7 List link command</h4>

<p><a name="index-g_t_0040option_007b_002d_002dlist_002dlink_007d-command-13"></a>Display files which will be linked.

<pre class="smallexample">     $ ghdl --list-link <var>primary_unit</var> [<var>secondary_unit</var>]
</pre>
   <p>This command is only available on GNU/Linux.

   <p>This command may be used only after a bind command.  GHDL displays all
the files which will be linked to create an executable.  This command is
intended to add object files in a link of a foreign program.

<div class="node">
<p><hr>
<a name="Check-syntax-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Analyze-and-elaborate-command">Analyze and elaborate command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#List-link-command">List link command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<h4 class="subsection">3.1.8 Check syntax command</h4>

<p><a name="index-checking-syntax-14"></a><a name="index-g_t_0040option_007b_002ds_007d-command-15"></a>Analyze files but do not generate code.

<pre class="smallexample">     $ ghdl -s [<var>options</var>] <var>files</var>
</pre>
   <p>This command may be used to check the syntax of files.  It does not update
the library.

<div class="node">
<p><hr>
<a name="Analyze-and-elaborate-command"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Check-syntax-command">Check syntax command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Building-commands">Building commands</a>

</div>

<h4 class="subsection">3.1.9 Analyze and elaborate command</h4>

<p><a name="index-Analyze-and-elaborate-command-16"></a><a name="index-g_t_0040option_007b_002dc_007d-command-17"></a>Analyze files and elaborate them at the same time.

   <p>On GNU/Linux:
<pre class="smallexample">     $ ghdl -c [<var>options</var>] <var>file</var>... -e <var>primary_unit</var> [<var>secondary_unit</var>]
</pre>
   <p>On Windows:
<pre class="smallexample">     $ ghdl -c [<var>options</var>] <var>file</var>... -r <var>primary_unit</var> [<var>secondary_unit</var>]
</pre>
   <p>This command combines analysis and elaboration: <var>file</var>s are analyzed and
the unit is then elaborated.  However, code is only generated during the
elaboration.  On Windows the simulation is launched.

   <p>To be more precise, the files are first parsed, and then the elaboration
drives the analysis.  Therefore, there is no analysis order, and you don't
need to care about it.

   <p>All the units of the files are put into the &lsquo;<samp><span class="samp">work</span></samp>&rsquo; library.  But, the
work library is neither read from disk nor saved.  Therefore, you must give
all the files of the &lsquo;<samp><span class="samp">work</span></samp>&rsquo; library your design needs.

   <p>The advantages over the traditional approach (analyze and then elaborate) are:
     <ul>
<li>The compilation cycle is achieved in one command. 
<li>Since the files are only parsed once, the compilation cycle may be faster. 
<li>You don't need to know an analysis order
<li>This command produces smaller executable, since unused units and subprograms
do not generate code. 
</ul>
   However, you should know that currently most of the time is spent in code
generation and the analyze and elaborate command generate code for all units
needed, even units of &lsquo;<samp><span class="samp">std</span></samp>&rsquo; and &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; libraries.  Therefore,
according to the design, the time for this command may be higher than the time
for the analyze command followed by the elaborate command.

   <p>This command is still experimental.  In case of problems, you should go back
to the traditional way.

<!-- node-name,  next,  previous,  up -->
<div class="node">
<p><hr>
<a name="GHDL-options"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Passing-options-to-other-programs">Passing options to other programs</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Building-commands">Building commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.2 GHDL options</h3>

<p><a name="index-IEEE-1164-18"></a><a name="index-g_t1164-19"></a><a name="index-IEEE-1076_002e3-20"></a><a name="index-g_t1076_002e3-21"></a><!-- document gcc options -->
Besides the options described below, <code>GHDL</code> passes any debugging options
(those that begin with <samp><span class="option">-g</span></samp>) and optimizations options (those that
begin with <samp><span class="option">-O</span></samp> or <samp><span class="option">-f</span></samp>) to <code>GCC</code>.  Refer to the <code>GCC</code>
manual for details.

     <dl>
<dt><code>--work=</code><var>NAME</var><dd><a name="index-g_t_0040option_007b_002d_002dwork_007d-switch-22"></a><a name="index-WORK-library-23"></a>Specify the name of the &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo; library.  Analyzed units are always
placed in the library logically named &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo;.  With this option,
you can set its name.  By default, the name is <var>work</var>.

     <p><code>GHDL</code> checks whether &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo; is a valid identifier.  Although being
more or less supported, the &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo; identifier should not be an
extended identifier, since the filesystem may prevent it from correctly
working (due to case sensitivity or forbidden characters in filenames).

     <p><code>VHDL</code> rules forbid you to add units to the &lsquo;<samp><span class="samp">std</span></samp>&rsquo; library. 
Furthermore, you should not put units in the &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; library.

     <br><dt><code>--workdir=</code><var>DIR</var><dd><a name="index-g_t_0040option_007b_002d_002dworkdir_007d-switch-24"></a>Specify the directory where the &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo; library is located.  When this
option is not present, the &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo; library is in the current
directory.  The object files created by the compiler are always placed
in the same directory as the &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo; library.

     <p>Use option <samp><span class="option">-P</span></samp> to specify where libraries other than &lsquo;<samp><span class="samp">WORK</span></samp>&rsquo;
are placed.

     <br><dt><code>--std=</code><var>STD</var><dd><a name="index-g_t_0040option_007b_002d_002dstd_007d-switch-25"></a>Specify the standard to use.  By default, the standard is &lsquo;<samp><span class="samp">93c</span></samp>&rsquo;, which
means VHDL-93 accepting VHDL-87 syntax.  For details on <var>STD</var> values see
<a href="#VHDL-standards">VHDL standards</a>.

     <br><dt><code>--ieee=</code><var>VER</var><dd><a name="index-g_t_0040option_007b_002d_002dieee_007d-switch-26"></a><a name="index-ieee-library-27"></a><a name="index-synopsys-library-28"></a><a name="index-mentor-library-29"></a>Select the <code>IEEE</code> library to use. <var>VER</var> must be one of:

          <dl>
<dt>&lsquo;<samp><span class="samp">none</span></samp>&rsquo;<dd>Do not supply an <code>IEEE</code> library.  Any library clause with the &lsquo;<samp><span class="samp">IEEE</span></samp>&rsquo;
identifier will fail, unless you have created by your own a library with
the <code>IEEE</code> name.

          <br><dt>&lsquo;<samp><span class="samp">standard</span></samp>&rsquo;<dd>Supply an <code>IEEE</code> library containing only packages defined by
<span class="sc">ieee</span> standards.  Currently, there are the multivalue logic system
packages &lsquo;<samp><span class="samp">std_logic_1164</span></samp>&rsquo; defined by IEEE 1164, the synthesis
packages , &lsquo;<samp><span class="samp">numeric_bit</span></samp>&rsquo; and &lsquo;<samp><span class="samp">numeric_std</span></samp>&rsquo; defined by IEEE
1076.3, and the <span class="sc">vital</span> packages &lsquo;<samp><span class="samp">vital_timing</span></samp>&rsquo; and
&lsquo;<samp><span class="samp">vital_primitives</span></samp>&rsquo;, defined by IEEE 1076.4.  The version of these
packages is defined by the VHDL standard used.  See <a href="#VITAL-packages">VITAL packages</a>,
for more details.

          <br><dt>&lsquo;<samp><span class="samp">synopsys</span></samp>&rsquo;<dd>Supply the former packages and the following additional packages:
&lsquo;<samp><span class="samp">std_logic_arith</span></samp>&rsquo;, &lsquo;<samp><span class="samp">std_logic_signed</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">std_logic_unsigned</span></samp>&rsquo;, &lsquo;<samp><span class="samp">std_logic_textio</span></samp>&rsquo;. 
<!-- @samp{std_logic_misc}. -->
These packages were created by some companies, and are popular.  However
they are not standard packages, and have been placed in the <code>IEEE</code>
library without the permission from the <span class="sc">ieee</span>.

          <br><dt>&lsquo;<samp><span class="samp">mentor</span></samp>&rsquo;<dd>Supply the standard packages and the following additional package:
&lsquo;<samp><span class="samp">std_logic_arith</span></samp>&rsquo;.  The package is a slight variation of a definitely
not standard but widely mis-used package. 
</dl>

     <p>To avoid errors, you must use the same <code>IEEE</code> library for all units of
your design, and during elaboration.

     <br><dt><code>-P</code><var>DIRECTORY</var><dd><a name="index-g_t_0040option_007b_002dP_007d-switch-30"></a>Add <var>DIRECTORY</var> to the end of the list of directories to be searched for
library files.

     <p>The <code>WORK</code> library is always searched in the path specified by the
<samp><span class="option">--workdir=</span></samp> option, or in the current directory if the latter
option is not specified.

     <br><dt><code>-fexplicit</code><dd><a name="index-g_t_0040option_007b_002dfexplicit_007d-switch-31"></a>When two operators are overloaded, give preference to the explicit declaration. 
This may be used to avoid the most common pitfall of the &lsquo;<samp><span class="samp">std_logic_arith</span></samp>&rsquo;
package.  See <a href="#IEEE-library-pitfalls">IEEE library pitfalls</a>, for an example.

     <p>This option is not set by default.  I don't think this option is a
good feature, because it breaks the encapsulation rule.  When set, an
operator can be silently overridden in another package.  You'd better to fix
your design and use the &lsquo;<samp><span class="samp">numeric_std</span></samp>&rsquo; package.

     <br><dt><code>--no-vital-checks</code><br><dt><code>--vital-checks</code><dd><a name="index-g_t_0040option_007b_002d_002dno_002dvital_002dchecks_007d-switch-32"></a><a name="index-g_t_0040option_007b_002d_002dvital_002dchecks_007d-switch-33"></a>Disable or enable checks of restriction on VITAL units.  Checks are enabled
by default.

     <p>Checks are performed only when a design unit is decorated by a VITAL attribute. 
The VITAL attributes are &lsquo;<samp><span class="samp">VITAL_Level0</span></samp>&rsquo; and &lsquo;<samp><span class="samp">VITAL_Level1</span></samp>&rsquo;, both
declared in the &lsquo;<samp><span class="samp">ieee.VITAL_Timing</span></samp>&rsquo; package.

     <p>Currently, VITAL checks are only partially implemented.  See <a href="#VHDL-restrictions-for-VITAL">VHDL restrictions for VITAL</a>, for more details.

     <br><dt><code>--syn-binding</code><dd><a name="index-g_t_0040option_007b_002d_002dsyn_002dbinding_007d-switch-34"></a>Use synthesizer rules for component binding.  During elaboration, if a
component is not bound to an entity using VHDL LRM rules, try to find
in any known library an entity whose name is the same as the component
name.

     <p>This rule is known as synthesizer rule.

     <p>There are two key points: normal VHDL LRM rules are tried first and
entities are searched only in known library.  A known library is a
library which has been named in your design.

     <p>This option is only useful during elaboration.

     <br><dt><code>--PREFIX=</code><var>PATH</var><dd><a name="index-g_t_0040option_007b_002d_002dPREFIX_007d-switch-35"></a>Use <var>PATH</var> as the prefix path to find commands and pre-installed (std and
ieee) libraries.

     <br><dt><code>--GHDL1=</code><var>COMMAND</var><dd><a name="index-g_t_0040option_007b_002d_002dGHLD1_007d-switch-36"></a>Use <var>COMMAND</var> as the command name for the compiler.  If <var>COMMAND</var> is
not a path, then it is search in the list of program directories.

     <br><dt><code>-v</code><dd>Be verbose.  For example, for analysis, elaboration and make commands, GHDL
displays the commands executed. 
</dl>

<div class="node">
<p><hr>
<a name="Passing-options-to-other-programs"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#GHDL-warnings">GHDL warnings</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#GHDL-options">GHDL options</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.3 Passing options to other programs</h3>

<p>These options are only available on GNU/Linux.

   <p>For many commands, <code>GHDL</code> acts as a driver: it invokes programs to perform
the command.  You can pass arbitrary options to these programs.

   <p>Both the compiler and the linker are in fact GCC programs.  See <a href="gcc.html#Invoking-GCC">GCC options</a>, for details on GCC
options.

     <dl>
<dt><code>-Wc,</code><var>OPTION</var><dd><a name="index-g_t_0040option_007b_002dW_007d-switch-37"></a>Pass <var>OPTION</var> as an option to the compiler.

     <br><dt><code>-Wa,</code><var>OPTION</var><dd><a name="index-g_t_0040option_007b_002dWa_007d-switch-38"></a>Pass <var>OPTION</var> as an option to the assembler.

     <br><dt><code>-Wl,</code><var>OPTION</var><dd><a name="index-g_t_0040option_007b_002dWl_007d-switch-39"></a>Pass <var>OPTION</var> as an option to the linker. 
</dl>

<div class="node">
<p><hr>
<a name="GHDL-warnings"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Rebuilding-commands">Rebuilding commands</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Passing-options-to-other-programs">Passing options to other programs</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.4 GHDL warnings</h3>

<p>Some constructions are not erroneous but dubious.  Warnings are diagnostic
messages that report such constructions.  Some warnings are reported only
during analysis, others during elaboration.

   <p>You could disable a warning by using the <samp><span class="option">--warn-no-XXX</span></samp>
instead of <samp><span class="option">--warn-XXX</span></samp>.

     <dl>
<dt><code>--warn-reserved</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002dreserved_007d-switch-40"></a>Emit a warning if an identifier is a reserved word in a later VHDL standard.

     <br><dt><code>--warn-default-binding</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002ddefault_002dbinding_007d-switch-41"></a>During analyze, warns if a component instantiation has neither
configuration specification nor default binding.  This may be useful if you
want to detect during analyze possibly unbound component if you don't use
configuration.  See <a href="#VHDL-standards">VHDL standards</a>, for more details about default binding
rules.

     <br><dt><code>--warn-binding</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002dbinding_007d-switch-42"></a>During elaboration, warns if a component instantiation is not bound
(and not explicitly left unbound).  Also warns if a port of an entity
is not bound in a configuration specification or in a component
configuration.  This warning is enabled by default, since default
binding rules are somewhat complex and an unbound component is most
often unexpected.

     <p>However, warnings are even emitted if a component instantiation is
inside a generate statement.  As a consequence, if you use the conditional
generate statement to select a component according to the implementation,
you will certainly get warnings.

     <br><dt><code>--warn-library</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002dlibrary_007d-switch-43"></a>Warns if a design unit replaces another design unit with the same name.

     <br><dt><code>--warn-vital-generic</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002dvital_002dgeneric_007d-switch-44"></a>Warns if a generic name of a vital entity is not a vital generic name.  This
is set by default.

     <br><dt><code>--warn-delayed-checks</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002ddelayed_002dchecks_007d-switch-45"></a>Warns for checks that cannot be done during analysis time and are
postponed to elaboration time.  This is because not all procedure
bodies are available during analysis (either because a package body
has not yet been analysed or because <code>GHDL</code> doesn't read not required
package bodies).

     <p>These are checks for no wait statement in a procedure called in a
sensitized process and checks for pure rules of a function.

     <br><dt><code>--warn-body</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002dbody_007d-switch-46"></a>Emit a warning if a package body which is not required is analyzed.  If a
package does not declare a subprogram or a deferred constant, the package
does not require a body.

     <br><dt><code>--warn-specs</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002dspecs_007d-switch-47"></a>Emit a warning if an all or others specification does not apply.

     <br><dt><code>--warn-unused</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002dunused_007d-switch-48"></a>Emit a warning when a subprogram is never used.

     <br><dt><code>--warn-error</code><dd><a name="index-g_t_0040option_007b_002d_002dwarn_002derror_007d-switch-49"></a>When this option is set, warnings are considered as errors.

   </dl>

<div class="node">
<p><hr>
<a name="Rebuilding-commands"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Library-commands">Library commands</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#GHDL-warnings">GHDL warnings</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.5 Rebuilding commands</h3>

<p>Analyzing and elaborating a design consisting in several files can be tricky,
due to dependencies.  GHDL has a few commands to rebuild a design.

<ul class="menu">
<li><a accesskey="1" href="#Import-command">Import command</a>
<li><a accesskey="2" href="#Make-command">Make command</a>
<li><a accesskey="3" href="#Generate-Makefile-command">Generate Makefile command</a>
</ul>

<div class="node">
<p><hr>
<a name="Import-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Make-command">Make command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Rebuilding-commands">Rebuilding commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Rebuilding-commands">Rebuilding commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.5.1 Import command</h4>

<p><a name="index-importing-files-50"></a><a name="index-g_t_0040option_007b_002di_007d-command-51"></a>Add files in the work design library.

<pre class="smallexample">     $ ghdl -i [<var>options</var>] <var>file</var>...
</pre>
   <p>All the files specified in the command line are scanned, parsed and added in
the libraries but as not yet analyzed.  No object files are created.

   <p>The purpose of this command is to localize design units in the design files. 
The make command will then be able to recursively build a hierarchy from
an entity name or a configuration name.

   <p>Since the files are parsed, there must be correct files.  However, since they
are not analyzed, many errors are tolerated by this command.

   <p>Note that all the files are added to the work library.  If you have many
libraries, you must use the command for each library.

<!-- Due to the LRM rules, there may be many analysis orders, producing -->
<!-- different results.  For example, if an entity has several architectures, -->
<!-- the last architecture analyzed is the default one in default binding -->
<!-- indications. -->
   <p>See <a href="#Make-command">Make command</a>, to actually build the design.

<div class="node">
<p><hr>
<a name="Make-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Generate-Makefile-command">Generate Makefile command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Import-command">Import command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Rebuilding-commands">Rebuilding commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.5.2 Make command</h4>

<p><a name="index-make-52"></a><a name="index-g_t_0040option_007b_002dm_007d-command-53"></a>
<pre class="smallexample">     $ ghdl -m [<var>options</var>] <var>primary</var> [<var>secondary</var>]
</pre>
   <p>Analyze automatically outdated files and elaborate a design.

   <p>The primary unit denoted by the <var>primary</var> argument must already be
known by the system, either because you have already analyzed it (even
if you have modified it) or because you have imported it.  GHDL analyzes
all outdated files.  A file may be outdated because it has been modified
(e.g. you just have edited it), or because a design unit contained in
the file depends on a unit which is outdated.  This rule is of course
recursive.

   <p>With the <samp><span class="option">-f</span></samp> (force) option, GHDL analyzes all the units of the
work library needed to create the design hierarchy.  Not outdated units
are recompiled.  This is useful if you want to compile a design hierarchy
with new compilation flags (for example, to add the <samp><span class="option">-g</span></samp>
debugging option).

   <p>The make command will only re-analyze design units in the work library. 
GHDL fails if it has to analyze an outdated unit from another library.

   <p>The purpose of this command is to be able to compile a design without prior
knowledge of file order.  In the VHDL model, some units must be analyzed
before others (e.g. an entity before its architecture).  It might be a
nightmare to analyze a full design of several files, if you don't have
the ordered list of file.  This command computes an analysis order.

   <p>The make command fails when a unit was not previously parsed.  For
example, if you split a file containing several design units into
several files, you must either import these new files or analyze them so
that GHDL knows in which file these units are.

   <p>The make command imports files which have been modified.  Then, a design
hierarchy is internally built as if no units are outdated.  Then, all outdated
design units, using the dependencies of the design hierarchy, are analyzed. 
If necessary, the design hierarchy is elaborated.

   <p>This is not perfect, since the default architecture (the most recently
analyzed one) may change while outdated design files are analyzed. In
such a case, re-run the make command of GHDL.

<!-- does not exists: @section GHDL robust make command -->
<div class="node">
<p><hr>
<a name="Generate-Makefile-command"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Make-command">Make command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Rebuilding-commands">Rebuilding commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.5.3 Generate Makefile command</h4>

<p><a name="index-g_t_0040option_007b_002d_002dgen_002dmakefile_007d-command-54"></a>Generate a Makefile to build a design unit.

<pre class="smallexample">     $ ghdl --gen-makefile [<var>options</var>] <var>primary</var> [<var>secondary</var>]
</pre>
   <p>This command works like the make command (see <a href="#Make-command">Make command</a>), but only a
makefile is generated on the standard output.

<div class="node">
<p><hr>
<a name="Library-commands"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Cross_002dreference-command">Cross-reference command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Rebuilding-commands">Rebuilding commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.6 Library commands</h3>

<p>GHDL has a few commands which act on a library.

<!-- node-name,  next,  previous,  up -->
<ul class="menu">
<li><a accesskey="1" href="#Directory-command">Directory command</a>
<li><a accesskey="2" href="#Clean-command">Clean command</a>
<li><a accesskey="3" href="#Remove-command">Remove command</a>
<li><a accesskey="4" href="#Copy-command">Copy command</a>
</ul>

<div class="node">
<p><hr>
<a name="Directory-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Clean-command">Clean command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Library-commands">Library commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Library-commands">Library commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.6.1 Directory command</h4>

<p><a name="index-displaying-library-55"></a><a name="index-g_t_0040option_007b_002dd_007d-command-56"></a>Display the name of the units contained in a design library.
<pre class="smallexample">     $ ghdl -d [<var>options</var>]
</pre>
   <p>The directory command, selected with the <var>-d</var> command line argument
displays the content of the work design library.  All options are
allowed, but only a few are meaningful: <samp><span class="option">--work=NAME</span></samp>,
<samp><span class="option">--workdir=PATH</span></samp> and <samp><span class="option">--std=VER</span></samp>.

<div class="node">
<p><hr>
<a name="Clean-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Remove-command">Remove command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Directory-command">Directory command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Library-commands">Library commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.6.2 Clean command</h4>

<p><a name="index-cleaning-57"></a><a name="index-g_t_0040option_007b_002d_002dclean_007d-command-58"></a>Remove object and executable files but keep the library.

<pre class="smallexample">     $ ghdl --clean [<var>options</var>]
</pre>
   <p>GHDL tries to remove any object, executable or temporary file it could
have created.  Source files are not removed.

   <p>There is no short command line form for this option to prevent accidental
clean up.

<div class="node">
<p><hr>
<a name="Remove-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Copy-command">Copy command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Clean-command">Clean command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Library-commands">Library commands</a>

</div>

<h4 class="subsection">3.6.3 Remove command</h4>

<p><a name="index-cleaning-all-59"></a><a name="index-g_t_0040option_007b_002d_002dremove_007d-command-60"></a>Do like the clean command but remove the library too.

<pre class="smallexample">     $ ghdl --remove [<var>options</var>]
</pre>
   <p>There is no short command line form for this option to prevent accidental
clean up.  Note that after removing a design library, the files are not
known anymore by GHDL.

<div class="node">
<p><hr>
<a name="Copy-command"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Remove-command">Remove command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Library-commands">Library commands</a>

</div>

<h4 class="subsection">3.6.4 Copy command</h4>

<p><a name="index-copying-library-61"></a><a name="index-g_t_0040option_007b_002d_002dcopy_007d-command-62"></a>Make a local copy of an existing library.

<pre class="smallexample">     $ ghdl --copy --work=<var>name</var> [<var>options</var>]
</pre>
   <p>Make a local copy of an existing library.  This is very useful if you want to
add unit to the &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; library:
<pre class="example">     $ ghdl --copy --work=ieee --ieee=synopsys
     $ ghdl -a --work=ieee numeric_unsigned.vhd
</pre>
   <div class="node">
<p><hr>
<a name="Cross-reference-command"></a>
<a name="Cross_002dreference-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#File-commands">File commands</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Library-commands">Library commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.7 Cross-reference command</h3>

<p>To easily navigate through your sources, you may generate cross-references.

<pre class="smallexample">     $ ghdl --xref-html [<var>options</var>] <var>file</var>...
</pre>
   <p>This command generates an html file for each <var>file</var> given in the command
line, with syntax highlighting and full cross-reference: every identifier is
a link to its declaration.  Besides, an index of the files is created too.

   <p>The set of <var>file</var> are analyzed, and then, if the analysis is
successful, html files are generated in the directory specified by the
<samp><span class="option">-o </span><var>dir</var></samp> option, or <samp><span class="file">html/</span></samp> directory by default.

   <p>If the <samp><span class="option">--format=html2</span></samp> is specified, then the generated html
files follow the HTML 2.0 standard, and colours are specified with
&lsquo;<samp><span class="samp">&lt;FONT&gt;</span></samp>&rsquo; tags.  However, colours are hard-coded.

   <p>If the <samp><span class="option">--format=css</span></samp> is specified, then the generated html files
follow the HTML 4.0 standard, and use the CSS-1 file <samp><span class="file">ghdl.css</span></samp> to
specify colours.  This file is generated only if it does not already exist (it
is never overwritten) and can be customized by the user to change colours or
appearance.  Refer to a generated file and its comments for more information.

<div class="node">
<p><hr>
<a name="File-commands"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Misc-commands">Misc commands</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Cross_002dreference-command">Cross-reference command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.8 File commands</h3>

<p>The following commands act on one or several files.  They do not analyze
files, therefore, they work even if a file has semantic errors.

<ul class="menu">
<li><a accesskey="1" href="#Pretty-print-command">Pretty print command</a>
<li><a accesskey="2" href="#Find-command">Find command</a>
<li><a accesskey="3" href="#Chop-command">Chop command</a>
<li><a accesskey="4" href="#Lines-command">Lines command</a>
</ul>

<div class="node">
<p><hr>
<a name="Pretty-print-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Find-command">Find command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#File-commands">File commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#File-commands">File commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.8.1 Pretty print command</h4>

<p><a name="index-g_t_0040option_007b_002d_002dpp_002dhtml_007d-command-63"></a><a name="index-pretty-printing-64"></a><a name="index-vhdl-to-html-65"></a>
Generate HTML on standard output from VHDL.

<pre class="smallexample">     $ ghdl --pp-html [<var>options</var>] <var>file</var>...
</pre>
   <p>The files are just scanned and an html file, with syntax highlighting is
generated on standard output.

   <p>Since the files are not even parsed, erroneous files or incomplete designs
can be pretty printed.

   <p>The style of the html file can be modified with the <samp><span class="option">--format=</span></samp> option. 
By default or when the <samp><span class="option">--format=html2</span></samp> option is specified, the output
is an HTML 2.0 file, with colours set through &lsquo;<samp><span class="samp">&lt;FONT&gt;</span></samp>&rsquo; tags.  When the
<samp><span class="option">--format=css</span></samp> option is specified, the output is an HTML 4.0 file,
with colours set through a CSS file, whose name is &lsquo;<samp><span class="samp">ghdl.css</span></samp>&rsquo;. 
See <a href="#Cross_002dreference-command">Cross-reference command</a>, for more details about this CSS file.

<div class="node">
<p><hr>
<a name="Find-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Chop-command">Chop command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Pretty-print-command">Pretty print command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#File-commands">File commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.8.2 Find command</h4>

<p><a name="index-g_t_0040option_007b_002df_007d-command-66"></a>Display the name of the design units in files.

<pre class="smallexample">     $ ghdl -f <var>file</var>...
</pre>
   <p>The files are scanned, parsed and the names of design units are displayed. 
Design units marked with two stars are candidate to be at the apex of a
design hierarchy.

<div class="node">
<p><hr>
<a name="Chop-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Lines-command">Lines command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Find-command">Find command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#File-commands">File commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.8.3 Chop command</h4>

<p><a name="index-g_t_0040option_007b_002d_002dchop_007d-command-67"></a>Chop (or split) files at design unit.

<pre class="smallexample">     $ ghdl --chop <var>files</var>
</pre>
   <p><code>GHDL</code> reads files, and writes a file in the current directory for
every design unit.

   <p>The filename of a design unit is build according to the unit.  For an
entity declaration, a package declaration or a configuration the file
name is <samp><span class="file">NAME.vhdl</span></samp>, where <var>NAME</var> is the name of the design
unit.  For a package body, the filename is <samp><span class="file">NAME-body.vhdl</span></samp>. 
Finally, for an architecture <var>ARCH</var> of an entity <var>ENTITY</var>, the
filename is <samp><span class="file">ENTITY-ARCH.vhdl</span></samp>.

   <p>Since the input files are parsed, this command aborts in case of syntax
error.  The command aborts too if a file to be written already exists.

   <p>Comments between design units are stored into the most adequate files.

   <p>This command may be useful to split big files, if your computer has not
enough memory to compile such files.  The size of the executable is
reduced too.

<div class="node">
<p><hr>
<a name="Lines-command"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Chop-command">Chop command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#File-commands">File commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.8.4 Lines command</h4>

<p><a name="index-g_t_0040option_007b_002d_002dlines_007d-command-68"></a>Display on the standard output lines of files preceded by line number.

<pre class="smallexample">     $ ghdl --lines <var>files</var>
</pre>
   <div class="node">
<p><hr>
<a name="Misc-commands"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Installation-Directory">Installation Directory</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#File-commands">File commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.9 Misc commands</h3>

<p>There are a few GHDL commands which are seldom useful.

<ul class="menu">
<li><a accesskey="1" href="#Help-command">Help command</a>
<li><a accesskey="2" href="#Dispconfig-command">Dispconfig command</a>
<li><a accesskey="3" href="#Disp-standard-command">Disp standard command</a>
<li><a accesskey="4" href="#Version-command">Version command</a>
</ul>

<div class="node">
<p><hr>
<a name="Help-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Dispconfig-command">Dispconfig command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Misc-commands">Misc commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Misc-commands">Misc commands</a>

</div>

<h4 class="subsection">3.9.1 Help command</h4>

<p><a name="index-g_t_0040option_007b_002dh_007d-command-69"></a><a name="index-g_t_0040option_007b_002d_002dhelp_007d-command-70"></a>Display (on the standard output) a short description of the all the commands
available.  If the help switch is followed by a command switch, then options
for this later command are displayed.

<pre class="smallexample">     $ ghdl --help
     $ ghdl -h
     $ ghdl -h <var>command</var>
</pre>
   <div class="node">
<p><hr>
<a name="Dispconfig-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Disp-standard-command">Disp standard command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Help-command">Help command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Misc-commands">Misc commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.9.2 Dispconfig command</h4>

<p><a name="index-g_t_0040option_007b_002d_002ddispconfig_007d-command-71"></a><a name="index-display-configuration-72"></a>Display the program paths and options used by GHDL.

<pre class="smallexample">     $ ghdl --dispconfig [<var>options</var>]
</pre>
   <p>This may be useful to track installation errors.

<div class="node">
<p><hr>
<a name="Disp-standard-command"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Version-command">Version command</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Dispconfig-command">Dispconfig command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Misc-commands">Misc commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.9.3 Disp standard command</h4>

<p><a name="index-g_t_0040option_007b_002d_002ddisp_002dstandard_007d-command-73"></a><a name="index-display-_0040samp_007bstd_002estandard_007d-74"></a>Display the &lsquo;<samp><span class="samp">std.standard</span></samp>&rsquo; package:

<pre class="smallexample">     $ ghdl --disp-standard [<var>options</var>]
</pre>
   <div class="node">
<p><hr>
<a name="Version-command"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Disp-standard-command">Disp standard command</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Misc-commands">Misc commands</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">3.9.4 Version command</h4>

<p><a name="index-g_t_0040option_007b_002d_002dversion_007d-command-75"></a><a name="index-version-76"></a>Display the <code>GHDL</code> version and exit.

<pre class="smallexample">     $ ghdl --version
</pre>
   <div class="node">
<p><hr>
<a name="Installation-Directory"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#IEEE-library-pitfalls">IEEE library pitfalls</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Misc-commands">Misc commands</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.10 Installation Directory</h3>

<!-- @code{GHDL} is installed with the @code{std} and @code{ieee} libraries. -->
<p>During analysis and elaboration <code>GHDL</code> may read the <code>std</code>
and <code>ieee</code> files.  The location of these files is based on the prefix,
which is (in priority order):
     <ol type=1 start=1>
<li>the <samp><span class="option">--PREFIX=</span></samp> command line option

     <li>the <var>GHDL_PREFIX</var> environment variable

     <li>a built-in default path.  It is a hard-coded path on GNU/Linux and the
value of the &lsquo;<samp><span class="samp">HKLM\Software\Ghdl\Install_Dir</span></samp>&rsquo; registry entry on Windows.
        </ol>

   <p>You should use the <samp><span class="option">--dispconfig</span></samp> command (see <a href="#Dispconfig-command">Dispconfig command</a> for details) to disp and debug installation problems.

<div class="node">
<p><hr>
<a name="IEEE-library-pitfalls"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#IEEE-math-packages">IEEE math packages</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Installation-Directory">Installation Directory</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.11 IEEE library pitfalls</h3>

<p>When you use options <samp><span class="option">--ieee=synopsys</span></samp> or <samp><span class="option">--ieee=mentor</span></samp>,
the <code>IEEE</code> library contains non standard packages such as
&lsquo;<samp><span class="samp">std_logic_arith</span></samp>&rsquo;. <!-- FIXME: ref -->

   <p>These packages are not standard because there are not described by an IEEE
standard, even if they have been put in the <code>IEEE</code> library.  Furthermore,
they are not really de-facto standard, because there are slight differences
between the packages of Mentor and those of Synopsys.

   <p>Furthermore, since they are not well-thought, their use has pitfalls.  For
example, this description has error during compilation:
<pre class="example">     library ieee;
     use ieee.std_logic_1164.all;
     
     --  <span class="roman">A counter from 0 to 10</span>.
     entity counter is
        port (val : out std_logic_vector (3 downto 0);
              ck : std_logic;
              rst : std_logic);
     end counter;
     
     library ieee;
     use ieee.std_logic_unsigned.all;
     
     architecture bad of counter
     is
        signal v : std_logic_vector (3 downto 0);
     begin
        process (ck, rst)
        begin
          if rst = '1' then
             v &lt;= x"0";
          elsif rising_edge (ck) then
             if v = "1010" then -- <span class="roman">Error</span>
                v &lt;= x"0";
             else
                v &lt;= v + 1;
             end if;
          end if;
        end process;
     
        val &lt;= v;
     end bad;
</pre>
   <p>When you analyze this design, GHDL does not accept it (too long lines
have been split for readability):
<pre class="smallexample">     $ ghdl -a --ieee=synopsys bad_counter.vhdl
     bad_counter.vhdl:13:14: operator "=" is overloaded
     bad_counter.vhdl:13:14: possible interpretations are:
     ../../libraries/ieee/std_logic_1164.v93:69:5: implicit function "="
         [std_logic_vector, std_logic_vector return boolean]
     ../../libraries/synopsys/std_logic_unsigned.vhdl:64:5: function "="
         [std_logic_vector, std_logic_vector return boolean]
     ../translate/ghdldrv/ghdl: compilation error
</pre>
   <p>Indeed, the <code>"="</code> operator is defined in both packages, and both
are visible at the place it is used.  The first declaration is an
implicit one, which occurs when the <code>std_logic_vector</code> type is
declared and is an element to element comparison, the second one is an
explicit declared function, with the semantic of an unsigned comparison.

   <p>With some analyser, the explicit declaration has priority over the implicit
declaration, and this design can be analyzed without error.  However, this
is not the rule given by the VHDL LRM, and since GHDL follows these rules,
it emits an error.

   <p>You can force GHDL to use this rule with the <samp><span class="option">-fexplicit</span></samp> option. 
See <a href="#GHDL-options">GHDL options</a>, for more details.

   <p>However it is easy to fix this error, by using a selected name:
<pre class="example">     library ieee;
     use ieee.std_logic_unsigned.all;
     
     architecture fixed_bad of counter
     is
        signal v : std_logic_vector (3 downto 0);
     begin
        process (ck, rst)
        begin
          if rst = '1' then
             v &lt;= x"0";
          elsif rising_edge (ck) then
             if ieee.std_logic_unsigned."=" (v, "1010") then
                v &lt;= x"0";
             else
                v &lt;= v + 1;
             end if;
          end if;
        end process;
     
        val &lt;= v;
     end fixed_bad;
</pre>
   <p>It is better to only use the standard packages defined by IEEE, which
provides the same functionalities:
<pre class="example">     library ieee;
     use ieee.numeric_std.all;
     
     architecture good of counter
     is
        signal v : unsigned (3 downto 0);
     begin
        process (ck, rst)
        begin
          if rst = '1' then
             v &lt;= x"0";
          elsif rising_edge (ck) then
             if v = "1010" then
                v &lt;= x"0";
             else
                v &lt;= v + 1;
             end if;
          end if;
        end process;
     
        val &lt;= std_logic_vector (v);
     end good;
</pre>
   <div class="node">
<p><hr>
<a name="IEEE-math-packages"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#IEEE-library-pitfalls">IEEE library pitfalls</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Invoking-GHDL">Invoking GHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">3.12 IEEE math packages</h3>

<p><a name="index-Math_005fReal-77"></a><a name="index-Math_005fComplex-78"></a>
The &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; math packages (&lsquo;<samp><span class="samp">math_real</span></samp>&rsquo; and
&lsquo;<samp><span class="samp">math_complex</span></samp>&rsquo;) provided with <code>GHDL</code> are not fully compliant with
the <code>IEEE</code> standard.  They are based on an early draft which can be
redistributed contrary to the final version of the package.

   <p>This is unfortunate and may generate errors as some declarations are missing
or have slightly changed.

   <p>If you have bought the standard from &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; then you can download
the sources of the packages from
<a href="http://standards.ieee.org/downloads/1076/1076.2-1996">http://standards.ieee.org/downloads/1076/1076.2-1996</a>
(unrestricted access).  You'd better to just download
<samp><span class="file">math_real.vhdl</span></samp>, <samp><span class="file">math_real-body.vhdl</span></samp>,
<samp><span class="file">math_complex.vhdl</span></samp> and <samp><span class="file">math_complex-body.vhdl</span></samp>.  The other files
are not necessary: the &lsquo;<samp><span class="samp">std_logic_1164</span></samp>&rsquo; package has to be updated for
<code>VHDL</code> 1993 (the <code>xnor</code> functions are commented out).

   <p>If you want to replace math packages for the standard version of the
<code>ieee</code> library, do:
<pre class="smallexample">     $ cp math_real.vhdl math_real-body.vhdl <samp><span class="file">ieee_install_dir</span></samp>
     $ cp math_complex.vhdl math_complex-body.vhdl <samp><span class="file">ieee_install_dir</span></samp>
     $ cd <samp><span class="file">ieee_install_dir</span></samp>
     $ ghdl -a --work=ieee math_real.vhdl math_real-body.vhdl
     $ ghdl -a --work=ieee math_complex.vhdl math_complex-body.vhdl
</pre>
   <p>(Replace <samp><span class="file">ieee_install_dir</span></samp> by the location of the <code>ieee</code> library as
displayed by &lsquo;<samp><span class="samp">ghdl -dispconfig</span></samp>&rsquo;).

   <p>You can repeat this for the &lsquo;<samp><span class="samp">synopsys</span></samp>&rsquo; version of the <code>ieee</code> library.

   <p>Don't forget that the math packages are only defined for the 1993 standard.

<div class="node">
<p><hr>
<a name="Simulation-and-runtime"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Invoking-GHDL">Invoking GHDL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h2 class="chapter">4 Simulation and runtime</h2>

<ul class="menu">
<li><a accesskey="1" href="#Simulation-options">Simulation options</a>
<li><a accesskey="2" href="#Debugging-VHDL-programs">Debugging VHDL programs</a>
</ul>

<div class="node">
<p><hr>
<a name="Simulation-options"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Debugging-VHDL-programs">Debugging VHDL programs</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Simulation-and-runtime">Simulation and runtime</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Simulation-and-runtime">Simulation and runtime</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">4.1 Simulation options</h3>

<p>In most system environments, it is possible to pass options while
invoking a program.  Contrary to most programming languages, there is no
standard method in VHDL to obtain the arguments or to set the exit
status.

   <p>In GHDL, it is impossible to pass parameters to your design.  A later version
could do it through the generics interfaces of the top entity.

   <p>However, the GHDL runtime behaviour can be modified with some options; for
example, it is possible to stop simulation after a certain time.

   <p>The exit status of the simulation is &lsquo;<samp><span class="samp">EXIT_SUCCESS</span></samp>&rsquo; (0) if the
simulation completes, or &lsquo;<samp><span class="samp">EXIT_FAILURE</span></samp>&rsquo; (1) in case of error
(assertion failure, overflow or any constraint error).

   <p>Here is the list of the most useful options.  Some debugging options are
also available, but not described here.  The &lsquo;<samp><span class="samp">--help</span></samp>&rsquo; options lists
all options available, including the debugging one.

     <dl>
<dt><code>--assert-level=</code><var>LEVEL</var><dd><a name="index-g_t_0040option_007b_002d_002dassert_002dlevel_007d-option-79"></a>Select the assertion level at which an assertion violation stops the
simulation.  <var>LEVEL</var> is the name from the <code>severity_level</code>
enumerated type defined in the <code>standard</code> package or the
&lsquo;<samp><span class="samp">none</span></samp>&rsquo; name.

     <p>By default, only assertion violation of severity level &lsquo;<samp><span class="samp">failure</span></samp>&rsquo;
stops the simulation.

     <p>For example, if <var>LEVEL</var> was &lsquo;<samp><span class="samp">warning</span></samp>&rsquo;, any assertion violation
with severity level &lsquo;<samp><span class="samp">warning</span></samp>&rsquo;, &lsquo;<samp><span class="samp">error</span></samp>&rsquo; or &lsquo;<samp><span class="samp">failure</span></samp>&rsquo; would
stop simulation, but the assertion violation at the &lsquo;<samp><span class="samp">note</span></samp>&rsquo; severity
level would only display a message.

     <p>&lsquo;<samp><span class="samp">--assert-level=none</span></samp>&rsquo; prevents any assertion violation to stop
simulation.

     <br><dt><code>--ieee-asserts=</code><var>POLICY</var><dd><a name="index-g_t_0040option_007b_002d_002dieee_002dasserts_007d-option-80"></a>Select how the assertions from &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; units are
handled. <var>POLICY</var> can be &lsquo;<samp><span class="samp">enable</span></samp>&rsquo; (the default),
&lsquo;<samp><span class="samp">disable</span></samp>&rsquo; which disables all assertion from &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; packages
and &lsquo;<samp><span class="samp">disable-at-0</span></samp>&rsquo; which disables only at start of simulation.

     <p>This option can be useful to avoid assertion message from
&lsquo;<samp><span class="samp">ieee.numeric_std</span></samp>&rsquo; (and other &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; packages).

     <br><dt><code>--stop-time=</code><var>TIME</var><dd><a name="index-g_t_0040option_007b_002d_002dstop_002dtime_007d-option-81"></a>Stop the simulation after <var>TIME</var>.  <var>TIME</var> is expressed as a time
value, <em>without</em> any space.  The time is the simulation time, not
the real clock time.

     <p>For examples:

     <pre class="smallexample">          $ ./my_design --stop-time=10ns
          $ ./my_design --stop-time=ps
</pre>
     <br><dt><code>--stop-delta=</code><var>N</var><dd><a name="index-g_t_0040option_007b_002d_002dstop_002ddelta_007d-option-82"></a>Stop the simulation after <var>N</var> delta cycles in the same current time. 
<!-- Delta cycles is a simulation technic used by VHDL to -->

     <br><dt><code>--disp-time</code><dd><a name="index-g_t_0040option_007b_002d_002ddisp_002dtime_007d-option-83"></a><a name="index-display-time-84"></a>Display the time and delta cycle number as simulation advances.

     <br><dt><code>--disp-tree[</code><var>=KIND</var><code>]</code><dd><a name="index-g_t_0040option_007b_002d_002ddisp_002dtree_007d-option-85"></a><a name="index-display-design-hierarchy-86"></a>Display the design hierarchy as a tree of instantiated design entities. 
This may be useful to understand the structure of a complex
design. <var>KIND</var> is optional, but if set must be one of:
          <dl>
<dt>&lsquo;<samp><span class="samp">none</span></samp>&rsquo;<dd>Do not display hierarchy.  Same as if the option was not present. 
<br><dt>&lsquo;<samp><span class="samp">inst</span></samp>&rsquo;<dd>Display entities, architectures, instances, blocks and generates statements. 
<br><dt>&lsquo;<samp><span class="samp">proc</span></samp>&rsquo;<dd>Like &lsquo;<samp><span class="samp">inst</span></samp>&rsquo; but also display processes. 
<br><dt>&lsquo;<samp><span class="samp">port</span></samp>&rsquo;<dd>Like &lsquo;<samp><span class="samp">proc</span></samp>&rsquo; but display ports and signals too. 
</dl>
     If <var>KIND</var> is not specified, the hierarchy is displayed with the
&lsquo;<samp><span class="samp">port</span></samp>&rsquo; mode.

     <br><dt><code>--no-run</code><dd><a name="index-g_t_0040option_007b_002d_002dno_002drun_007d-option-87"></a>Do not simulate, only elaborate.  This may be used with
<samp><span class="option">--disp-tree</span></samp> to display the tree without simulating the whole
design.

     <br><dt><code>--vcd=</code><var>FILENAME</var><br><dt><code>--vcdgz=</code><var>FILENAME</var><dd><a name="index-g_t_0040option_007b_002d_002dvcd_007d-option-88"></a><a name="index-g_t_0040option_007b_002d_002dvcdgz_007d-option-89"></a><a name="index-vcd-90"></a><a name="index-value-change-dump-91"></a><a name="index-dump-of-signals-92"></a><samp><span class="option">--vcd</span></samp> dumps into the VCD file <var>FILENAME</var> the signal
values before each non-delta cycle.  If <var>FILENAME</var> is &lsquo;<samp><span class="samp">-</span></samp>&rsquo;,
then the standard output is used, otherwise a file is created or
overwritten.

     <p>The <samp><span class="option">--vcdgz</span></samp> option is the same as the <samp><span class="option">--vcd</span></samp> option,
but the output is compressed using the <code>zlib</code> (<code>gzip</code>
compression).  However, you can't use the &lsquo;<samp><span class="samp">-</span></samp>&rsquo; filename. 
Furthermore, only one VCD file can be written.

     <p><dfn>VCD</dfn> (value change dump) is a file format defined
by the <code>verilog</code> standard and used by virtually any wave viewer.

     <p>Since it comes from <code>verilog</code>, only a few VHDL types can be dumped.  GHDL
dumps only signals whose base type is of the following:
          <ul>
<li>types defined in the &lsquo;<samp><span class="samp">std.standard</span></samp>&rsquo; package:
               <ul>
<li>&lsquo;<samp><span class="samp">bit</span></samp>&rsquo;
<li>&lsquo;<samp><span class="samp">bit_vector</span></samp>&rsquo;
</ul>
          <li>types defined in the &lsquo;<samp><span class="samp">ieee.std_logic_1164</span></samp>&rsquo; package:
               <ul>
<li>&lsquo;<samp><span class="samp">std_ulogic</span></samp>&rsquo;
<li>&lsquo;<samp><span class="samp">std_logic</span></samp>&rsquo; (because it is a subtype of &lsquo;<samp><span class="samp">std_ulogic</span></samp>&rsquo;)
<li>&lsquo;<samp><span class="samp">std_ulogic_vector</span></samp>&rsquo;
<li>&lsquo;<samp><span class="samp">std_logic_vector</span></samp>&rsquo;
</ul>
          <li>any integer type
</ul>

     <p>I have successfully used <code>gtkwave</code> to view VCD files.

     <p>Currently, there is no way to select signals to be dumped: all signals are
dumped, which can generate big files.

     <p>It is very unfortunate there is no standard or well-known wave file
format supporting VHDL types.  If you are aware of such a free format,
please mail me (see <a href="#Reporting-bugs">Reporting bugs</a>).

     <br><dt><code>--wave=</code><var>FILENAME</var><dd><a name="index-g_t_0040option_007b_002d_002dwave_007d-option-93"></a>Write the waveforms into a <code>ghw</code> (GHdl Waveform) file.  Currently, all
the signals are dumped into the waveform file, you cannot select a hierarchy
of signals to be dumped.

     <p>The format of this file was defined by myself and is not yet completely fixed. 
It may change slightly.

     <p>There is a patch against <code>gtkwave 1.3.72</code> on the ghdl website at
<a href="ghdl.free.fr">ghdl.free.fr</a>, so that it can read such files.

     <p>Contrary to VCD files, any VHDL type can be dumped into a GHW file.

     <br><dt><code>--sdf=</code><var>PATH</var><code>=</code><var>FILENAME</var><br><dt><code>--sdf=min=</code><var>PATH</var><code>=</code><var>FILENAME</var><br><dt><code>--sdf=typ=</code><var>PATH</var><code>=</code><var>FILENAME</var><br><dt><code>--sdf=max=</code><var>PATH</var><code>=</code><var>FILENAME</var><dd><a name="index-g_t_0040option_007b_002d_002dsdf_007d-option-94"></a>Do VITAL annotation on <var>PATH</var> with SDF file <var>FILENAME</var>.

     <p><var>PATH</var> is a path of instances, separated with &lsquo;<samp><span class="samp">.</span></samp>&rsquo; or &lsquo;<samp><span class="samp">/</span></samp>&rsquo;. 
Any separator can be used.  Instances are component instantiation labels,
generate labels or block labels.  Currently, you cannot use an indexed name.

     <p>If the option contains a type of delay, that is <samp><span class="option">min=</span></samp>,
<samp><span class="option">typ=</span></samp> or <samp><span class="option">max=</span></samp>, the annotator use respectively minimum,
typical or maximum values.  If the option does not contain a type of delay,
the annotator use the typical delay.

     <p>See <a href="#Backannotation">Backannotation</a>, for more details.

     <br><dt><code>--stack-max-size=</code><var>SIZE</var><dd><a name="index-g_t_0040option_007b_002d_002dstack_002dmax_002dsize_007d-option-95"></a>Set the maximum size in bytes of the non-sensitized processes stacks.

     <p>If the value <var>SIZE</var> is followed (without any space) by the &lsquo;<samp><span class="samp">k</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">K</span></samp>&rsquo;, &lsquo;<samp><span class="samp">kb</span></samp>&rsquo;, &lsquo;<samp><span class="samp">Kb</span></samp>&rsquo;, &lsquo;<samp><span class="samp">ko</span></samp>&rsquo; or &lsquo;<samp><span class="samp">Ko</span></samp>&rsquo; multiplier, then
the size is the numeric value multiplied by 1024.

     <p>If the value <var>SIZE</var> is followed (without any space) by the &lsquo;<samp><span class="samp">m</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">M</span></samp>&rsquo;, &lsquo;<samp><span class="samp">mb</span></samp>&rsquo;, &lsquo;<samp><span class="samp">Mb</span></samp>&rsquo;, &lsquo;<samp><span class="samp">mo</span></samp>&rsquo; or &lsquo;<samp><span class="samp">Mo</span></samp>&rsquo; multiplier, then
the size is the numeric value multiplied by 1024 * 1024 = 1048576.

     <p>Each non-sensitized process has its own stack, while the sensitized processes
share the same and main stack.  This stack is the stack created by the
operating system.

     <p>Using too small stacks may result in simulation failure due to lack of memory. 
Using too big stacks may reduce the maximum number of processes.

     <br><dt><code>--stack-size=</code><var>SIZE</var><dd><a name="index-g_t_0040option_007b_002d_002dstack_002dsize_007d-option-96"></a>Set the initial size in bytes of the non-sensitized processes stack. 
The <var>SIZE</var> value has the same format as the previous option.

     <p>The stack of the non-sensitized processes grows until reaching the
maximum size limit.

     <br><dt><code>--help</code><dd>Display a short description of the options accepted by the runtime library. 
</dl>

<div class="node">
<p><hr>
<a name="Debugging-VHDL-programs"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Simulation-options">Simulation options</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Simulation-and-runtime">Simulation and runtime</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">4.2 Debugging VHDL programs</h3>

<p><a name="index-debugging-97"></a><a name="index-g_t_0040code_007b_005f_005fghdl_005ffatal_007d-98"></a>Debugging VHDL programs using <code>GDB</code> is possible only on GNU/Linux systems.

   <p><code>GDB</code> is a general purpose debugger for programs compiled by <code>GCC</code>. 
Currently, there is no VHDL support for <code>GDB</code>.  It may be difficult
to inspect variables or signals in <code>GDB</code>, however, <code>GDB</code> is
still able to display the stack frame in case of error or to set a breakpoint
at a specified line.

   <p><code>GDB</code> can be useful to precisely catch a runtime error, such as indexing
an array beyond its bounds.  All error check subprograms call the
<code>__ghdl_fatal</code> procedure.  Therefore, to catch runtime error, set
a breakpoint like this:
<pre class="smallexample">     (gdb) break __ghdl_fatal
</pre>
   <p>When the breakpoint is hit, use the <code>where</code> or <code>bt</code> command to
display the stack frames.

<div class="node">
<p><hr>
<a name="GHDL-implementation-of-VHDL"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Simulation-and-runtime">Simulation and runtime</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h2 class="chapter">5 GHDL implementation of VHDL</h2>

<p>This chapter describes several implementation defined aspect of VHDL in GHDL.

<ul class="menu">
<li><a accesskey="1" href="#VHDL-standards">VHDL standards</a>
<li><a accesskey="2" href="#Source-representation">Source representation</a>
<li><a accesskey="3" href="#Library-database">Library database</a>
<li><a accesskey="4" href="#VHDL-files-format">VHDL files format</a>
<li><a accesskey="5" href="#Top-entity">Top entity</a>
<li><a accesskey="6" href="#Using-vendor-libraries">Using vendor libraries</a>
<li><a accesskey="7" href="#Using-ieee_002emath_005freal-or-ieee_002emath_005fcomplex">Using ieee.math_real or ieee.math_complex</a>
<li><a accesskey="8" href="#Interfacing-to-other-languages">Interfacing to other languages</a>
</ul>

<div class="node">
<p><hr>
<a name="VHDL-standards"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Source-representation">Source representation</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">5.1 VHDL standards</h3>

<p><a name="index-VHDL-standards-99"></a><a name="index-IEEE-1076-100"></a><a name="index-IEEE-1076a-101"></a><a name="index-g_t1076-102"></a><a name="index-g_t1076a-103"></a><a name="index-v87-104"></a><a name="index-v93-105"></a><a name="index-v93c-106"></a><a name="index-v00-107"></a><a name="index-v02-108"></a>This is very unfortunate, but there are many versions of the VHDL language.

   <p>The VHDL language was first standardized in 1987 by IEEE as IEEE 1076-1987, and
is commonly referred as VHDL-87. This is certainly the most important version,
since most of the VHDL tools are still based on this standard.

   <p>Various problems of this first standard have been analyzed by experts groups
to give reasonable ways of interpreting the unclear portions of the standard.

   <p>VHDL was revised in 1993 by IEEE as IEEE 1076-1993.  This revision is still
well-known.

   <p>Unfortunately, VHDL-93 is not fully compatible with VHDL-87, i.e. some perfectly
valid VHDL-87 programs are invalid VHDL-93 programs.  Here are some of the
reasons:

     <ul>
<li>the syntax of file declaration has changed (this is the most visible source
of incompatibility),
<li>new keywords were introduced (group, impure, inertial, literal,
postponed, pure, reject, rol, ror, shared, sla, sll, sra, srl,
unaffected, xnor),
<li>some dynamic behaviours have changed (the concatenation is one of them),
<li>rules have been added. 
</ul>

   <p>Shared variables were replaced by protected types in the 2000 revision of
the VHDL standard.  This modification is also known as 1076a.  Note that this
standard is not fully backward compatible with VHDL-93, since the type of a
shared variable must now be a protected type (there was no such restriction
before).

   <p>Minors corrections were added by the 2002 revision of the VHDL standard.  This
revision is not fully backward compatible with VHDL-00 since, for example,
the value of the <code>'instance_name</code> attribute has slightly changed.

   <p>You can select the VHDL standard expected by GHDL with the
&lsquo;<samp><span class="samp">--std=VER</span></samp>&rsquo; option, where <var>VER</var> is one of the left column of the
table below:

     <dl>
<dt>&lsquo;<samp><span class="samp">87</span></samp>&rsquo;<dd>Select VHDL-87 standard as defined by IEEE 1076-1987.  LRM bugs corrected by
later revisions are taken into account. 
<br><dt>&lsquo;<samp><span class="samp">93</span></samp>&rsquo;<dd>Select VHDL-93; VHDL-87 file declarations are not accepted. 
<br><dt>&lsquo;<samp><span class="samp">93c</span></samp>&rsquo;<dd>Select VHDL-93 standard with relaxed rules:
          <ul>
<li>VHDL-87 file declarations are accepted;
<li>default binding indication rules of VHDL-02 are used.  Default binding rules
are often used, but they are particularly obscure before VHDL-02. 
</ul>
     <br><dt>&lsquo;<samp><span class="samp">00</span></samp>&rsquo;<dd>Select VHDL-2000 standard, which adds protected types. 
<br><dt>&lsquo;<samp><span class="samp">02</span></samp>&rsquo;<dd>Select VHDL-2002 standard (partially implemented). 
</dl>

   <p>You cannot mix VHDL-87 and VHDL-93 units.  A design hierarchy must have been
completely analyzed using either the 87 or the 93 version of the VHDL standard.

<div class="node">
<p><hr>
<a name="Source-representation"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Library-database">Library database</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#VHDL-standards">VHDL standards</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">5.2 Source representation</h3>

<p>According to the VHDL standard, design units (i.e. entities,
architectures, packages, package bodies and configurations) may be
independently analyzed.

   <p>Several design units may be grouped into a design file.

   <p>In GHDL, a system file represents a design file.  That is, a file compiled by
GHDL may contain one or more design units.

   <p>It is common to have several design units in a design file.

   <p>GHDL does not impose any restriction on the name of a design file
(except that the filename may not contain any control character or
spaces).

   <p>GHDL do not keep a binary representation of the design units analyzed like
other VHDL analyzers.  The sources of the design units are re-read when
needed (for example, an entity is re-read when one of its architecture is
analyzed).  Therefore, if you delete or modify a source file of a unit
analyzed, GHDL will refuse to use it.

<div class="node">
<p><hr>
<a name="Library-database"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#VHDL-files-format">VHDL files format</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Source-representation">Source representation</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>

</div>

<h3 class="section">5.3 Library database</h3>

<p>Each design unit analyzed is placed into a design library.  By default,
the name of this design library is &lsquo;<samp><span class="samp">work</span></samp>&rsquo;; however, this can be
changed with the <samp><span class="option">--work=NAME</span></samp> option of GHDL.

   <p>To keep the list of design units in a design library, GHDL creates
library files.  The name of these files is &lsquo;<samp><span class="samp">NAME-objVER.cf</span></samp>&rsquo;, where
<var>NAME</var> is the name of the library, and <var>VER</var> the VHDL version (87
or 93) used to analyze the design units.

   <p>You don't have to know how to read a library file.  You can display it
using the <samp><span class="option">-d</span></samp> of <code>ghdl</code>.  The file contains the name of the
design units, as well as the location and the dependencies.

   <p>The format may change with the next version of GHDL.

<div class="node">
<p><hr>
<a name="VHDL-files-format"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Top-entity">Top entity</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Library-database">Library database</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">5.4 VHDL files format</h3>

<p><a name="index-file-format-109"></a><a name="index-logical-name-110"></a>VHDL has features to handle files.

   <p>GHDL associates a file logical name (the VHDL filename) to an operating
system filename.  The logical name &lsquo;<samp><span class="samp">STD_INPUT</span></samp>&rsquo; is associated to
the standard input as defined by &lsquo;<samp><span class="samp">stdin</span></samp>&rsquo; stream of the C library,
while the logical name &lsquo;<samp><span class="samp">STD_OUTPUT</span></samp>&rsquo; is associated to the standard
output, as defined by the &lsquo;<samp><span class="samp">stdout</span></samp>&rsquo; stream of the C library.  Other
logical name are directly mapped to a filename as defined by the first
(&lsquo;<samp><span class="samp">path</span></samp>&rsquo;) argument of the &lsquo;<samp><span class="samp">fopen</span></samp>&rsquo; function of the C library. 
For a binary file, the &lsquo;<samp><span class="samp">b</span></samp>&rsquo; character is appended to the mode argument
(binary mode).

   <p>If multiple file objects are associated with the same external file, a stream
is created for each object, except for the standard input or output.

   <p>GHDL has no internal restrictions on the number of file objects that are
associated at one time with a given external file, but the operating system
may restrict the maximum number of file open at the same time.

   <p>For more details about these point, please refer to your operation system
documentation.

<!-- tell more about possible errors. -->
   <p>There are two kinds of files: binary or text files.

   <p>Text files are files of type &lsquo;<samp><span class="samp">std.textio.text</span></samp>&rsquo;.  The format is the
same as the format of any ascii file.  In VHDL-87, only the first 128
characters (7 bits) are allowed, since the character type has only 128
literals.  The end of line is system dependent.  Note that the stdio
functions with the text mode are used to handle text files: the fgets
function is used to read lines.  Please, refer to the manual of your C
library for more information.

   <p>There are two kind of binary files, according to the type mark of the
file.  According to the VHDL standard, binary files must be read using
the same type they are written.

   <p>If the type mark is a non-composite type (integer, floating type
enumeration, physical), the file is a raw stream:
elements are read or written using the same format as is used to represent
the data in memory.  This is highly non-portable, but you should be able
to read file written by a non-<code>GHDL</code> program.

   <p>If the type mark is a composite type (record or array), the file is composed
of a 2 lines signature, followed by a raw stream.

<div class="node">
<p><hr>
<a name="Top-entity"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Using-vendor-libraries">Using vendor libraries</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#VHDL-files-format">VHDL files format</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">5.5 Top entity</h3>

<p>There are some restrictions on the entity being at the apex of a design
hierarchy:

     <ul>
<li>The generic must have a default value, and the value of a generic is its
default value;
<li>The ports type must be constrained. 
</ul>

<div class="node">
<p><hr>
<a name="Using-vendor-libraries"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Using-ieee_002emath_005freal-or-ieee_002emath_005fcomplex">Using ieee.math_real or ieee.math_complex</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Top-entity">Top entity</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">5.6 Using vendor libraries</h3>

<p>Many vendors libraries have been analyzed with GHDL.  There are
usually no problems.  Be sure to use the <samp><span class="option">--work=</span></samp> option. 
However, some problems have been encountered.

   <p>GHDL follows the VHDL LRM (the manual which defines VHDL) more
strictly than other VHDL tools.  You could try to relax the
restrictions by using the <samp><span class="option">--std=93c</span></samp>, <samp><span class="option">-fexplicit</span></samp> and
<samp><span class="option">--warn-no-vital-generic</span></samp>.

   <p>Even with these relaxations, some broken libraries may fail.

   <p>For example, <code>unisim_VITAL.vhd</code> from <code>Xilinx</code> can't be
compiled because lines such as:
<pre class="smallexample">      variable Write_A_Write_B : memory_collision_type := Write_A_Write_B;
      variable Read_A_Write_B  : memory_collision_type := Read_A_Write_B;
</pre>
   <p>(there are 6 such lines). 
According to VHDL visibility rules, &lsquo;<samp><span class="samp">Write_A_Write_B</span></samp>&rsquo; cannot be used
while it is defined.  This is very logical because it prevents from silly
declarations such as
<pre class="smallexample">       constant k : natural := 2 * k;
</pre>
   <p>This files must be modified.  Fortunately, in the example the variables
are never written.  So it is enough to remove them.

<div class="node">
<p><hr>
<a name="Using-ieee.math_real-or-ieee.math_complex"></a>
<a name="Using-ieee_002emath_005freal-or-ieee_002emath_005fcomplex"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Interfacing-to-other-languages">Interfacing to other languages</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Using-vendor-libraries">Using vendor libraries</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">5.7 Using ieee.math_real or ieee.math_complex</h3>

<p><a name="index-math_005freal-111"></a><a name="index-math_005fcomplex-112"></a>Contrary to other &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; libraries, the math packages sources are not
freely available.  The sources provided with GHDL are based on an early draft
and use the C libraries.  As a consequence, you should link your design
with the &lsquo;<samp><span class="samp">libm.a</span></samp>&rsquo; library using the <samp><span class="option">-Wl,</span></samp> option like:
<pre class="smallexample">     $ ghdl -e -Wl,-lm my_design
</pre>
   <p>Please, refer to your system manual for more details.

   <p>Please also note that the &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; libraries are not the same as the drafts.

   <p>If you really need the &lsquo;<samp><span class="samp">ieee</span></samp>&rsquo; math libraries, they are available on the
web, but they cannot be included in GHDL.

<div class="node">
<p><hr>
<a name="Interfacing-to-other-languages"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Using-ieee_002emath_005freal-or-ieee_002emath_005fcomplex">Using ieee.math_real or ieee.math_complex</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">5.8 Interfacing to other languages</h3>

<p><a name="index-interfacing-113"></a><a name="index-other-languages-114"></a><a name="index-foreign-115"></a><a name="index-VHPI-116"></a><a name="index-VHPIDIRECT-117"></a>Interfacing with foreign languages is possible only on GNU/Linux systems.

   <p>You can define a subprogram in a foreign language (such as <code>C</code> or
<code>Ada</code>) and import it in a VHDL design.

<h4 class="subsection">5.8.1 Foreign declarations</h4>

<p>Only subprograms (functions or procedures) can be imported, using the foreign
attribute.  In this example, the <code>sin</code> function is imported:

<pre class="example">     package math is
       function sin (v : real) return real;
       attribute foreign of sin : function is "VHPIDIRECT sin";
     end math;
     
     package body math is
       function sin (v : real) return real is
       begin
         assert false severity failure;
       end sin;
     end math;
</pre>
   <p>A subprogram is made foreign if the <var>foreign</var> attribute decorates
it.  This attribute is declared in the 1993 revision of the
&lsquo;<samp><span class="samp">std.standard</span></samp>&rsquo; package.  Therefore, you cannot use this feature in
VHDL 1987.

   <p>The decoration is achieved through an attribute specification.  The
attribute specification must be in the same declarative part as the
subprogram and must be after it.  This is a general rule for specifications. 
The value of the specification must be a locally static string.

   <p>Even when a subprogram is foreign, its body must be present.  However, since
it won't be called, you can made it empty or simply but an assertion.

   <p>The value of the attribute must start with &lsquo;<samp><span class="samp">VHPIDIRECT </span></samp>&rsquo; (an
upper-case keyword followed by one or more blanks).  The linkage name of the
subprogram follows.

<ul class="menu">
<li><a accesskey="1" href="#Restrictions-on-foreign-declarations">Restrictions on foreign declarations</a>
<li><a accesskey="2" href="#Linking-with-foreign-object-files">Linking with foreign object files</a>
<li><a accesskey="3" href="#Starting-a-simulation-from-a-foreign-program">Starting a simulation from a foreign program</a>
<li><a accesskey="4" href="#Linking-with-Ada">Linking with Ada</a>
<li><a accesskey="5" href="#Using-GRT-from-Ada">Using GRT from Ada</a>
</ul>

<div class="node">
<p><hr>
<a name="Restrictions-on-foreign-declarations"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Linking-with-foreign-object-files">Linking with foreign object files</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Interfacing-to-other-languages">Interfacing to other languages</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Interfacing-to-other-languages">Interfacing to other languages</a>

</div>

<h4 class="subsection">5.8.2 Restrictions on foreign declarations</h4>

<p>Any subprogram can be imported.  GHDL puts no restrictions on foreign
subprograms.  However, the representation of a type or of an interface in a
foreign language may be obscure.  Most of non-composite types are easily imported:
     <dl>
<dt>&lsquo;<samp><span class="samp">integer types</span></samp>&rsquo;<dd>They are represented on a 32 bits word.  This generally corresponds to
<code>int</code> for <code>C</code> or <code>Integer</code> for <code>Ada</code>. 
<br><dt>&lsquo;<samp><span class="samp">physical types</span></samp>&rsquo;<dd>They are represented on a 64 bits word.  This generally corresponds to the
<code>long long</code> for <code>C</code> or <code>Long_Long_Integer</code> for <code>Ada</code>. 
<br><dt>&lsquo;<samp><span class="samp">floating point types</span></samp>&rsquo;<dd>They are represented on a 64 bits floating point word.  This generally
corresponds to <code>double</code> for <code>C</code> or <code>Long_Float</code> for <code>Ada</code>. 
<br><dt>&lsquo;<samp><span class="samp">enumeration types</span></samp>&rsquo;<dd>They are represented on 8 bits or 32 bits word, if the number of literals is
greater than 256.  There is no corresponding C types, since arguments are
not promoted. 
</dl>

   <p>Non-composite types are passed by value.  For the <code>in</code> mode, this
corresponds to the <code>C</code> or <code>Ada</code> mechanism.  The <code>out</code> and
<code>inout</code> interfaces of non-composite types are gathered in a record
and this record is passed by reference as the first argument to the
subprogram.  As a consequence, you shouldn't use <code>in</code> and
<code>inout</code> modes in foreign subprograms, since they are not portable.

   <p>Records are represented like a <code>C</code> structure and are passed by reference
to subprograms.

   <p>Arrays with static bounds are represented like a <code>C</code> array, whose
length is the number of elements, and are passed by reference to subprograms.

   <p>Unconstrained array are represented by a fat pointer.  Do not use unconstrained
arrays in foreign subprograms.

   <p>Accesses to an unconstrained array is a fat pointer.  Other accesses correspond to an address and are passed to a subprogram like other non-composite types.

   <p>Files are represented by a 32 bits word, which corresponds to an index
in a table.

<div class="node">
<p><hr>
<a name="Linking-with-foreign-object-files"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Starting-a-simulation-from-a-foreign-program">Starting a simulation from a foreign program</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Restrictions-on-foreign-declarations">Restrictions on foreign declarations</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Interfacing-to-other-languages">Interfacing to other languages</a>

</div>

<h4 class="subsection">5.8.3 Linking with foreign object files</h4>

<p>You may add additional files or options during the link using the
<samp><span class="option">-Wl,</span></samp> of <code>GHDL</code>, as described in <a href="#Elaboration-command">Elaboration command</a>. 
For example:

<pre class="example">     $ ghdl -e -Wl,-lm math_tb
</pre>
   <p>will create the <samp><span class="file">math_tb</span></samp> executable with the <samp><span class="file">lm</span></samp> (mathematical)
library.

   <p>Note the <samp><span class="file">c</span></samp> library is always linked with an executable.

<div class="node">
<p><hr>
<a name="Starting-a-simulation-from-a-foreign-program"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Linking-with-Ada">Linking with Ada</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Linking-with-foreign-object-files">Linking with foreign object files</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Interfacing-to-other-languages">Interfacing to other languages</a>

</div>

<h4 class="subsection">5.8.4 Starting a simulation from a foreign program</h4>

<p>You may run your design from an external program.  You just have to call
the &lsquo;<samp><span class="samp">ghdl_main</span></samp>&rsquo; function which can be defined:

   <p>in C:
<pre class="smallexample">     extern int ghdl_main (int argc, char **argv);
</pre>
   <p>in Ada:
<pre class="smallexample">     with System;
     ...
     function Ghdl_Main (Argc : Integer; Argv : System.Address)
        return Integer;
     pragma import (C, Ghdl_Main, "ghdl_main");
</pre>
   <p>This function must be called once, and returns 0 at the end of the simulation. 
In case of failure, this function does not return.  This has to be fixed.

<div class="node">
<p><hr>
<a name="Linking-with-Ada"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Using-GRT-from-Ada">Using GRT from Ada</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Starting-a-simulation-from-a-foreign-program">Starting a simulation from a foreign program</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Interfacing-to-other-languages">Interfacing to other languages</a>

</div>

<h4 class="subsection">5.8.5 Linking with Ada</h4>

<p>As explained previously in <a href="#Starting-a-simulation-from-a-foreign-program">Starting a simulation from a foreign program</a>,
you can start a simulation from an <code>Ada</code> program.  However the build
process is not trivial: you have to elaborate your <code>Ada</code> program and your
<code>VHDL</code> design.

   <p>First, you have to analyze all your design files.  In this example, we
suppose there is only one design file, <samp><span class="file">design.vhdl</span></samp>.
<pre class="smallexample">     $ ghdl -a design.vhdl
</pre>
   <p>Then, bind your design.  In this example, we suppose the entity at the
design apex is &lsquo;<samp><span class="samp">design</span></samp>&rsquo;.
<pre class="smallexample">     $ ghdl --bind design
</pre>
   <p>Finally, compile, bind your <code>Ada</code> program at link it with your <code>VHDL</code>
design:
<pre class="smallexample">     $ gnatmake my_prog -largs `ghdl --list-link design`
</pre>
   <div class="node">
<p><hr>
<a name="Using-GRT-from-Ada"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Linking-with-Ada">Linking with Ada</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Interfacing-to-other-languages">Interfacing to other languages</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">5.8.6 Using GRT from Ada</h4>

<blockquote>
<b>Warning:</b> This topic is only for advanced users knowing how to use <code>Ada</code>
and <code>GNAT</code>.  This is provided only for reference, I have tested
this once before releasing <code>GHDL</code> 0.19 but this is not checked at
each release. 
</blockquote>

   <p>The simulator kernel of <code>GHDL</code> named <dfn>GRT</dfn> is written in
<code>Ada95</code> and contains a very light and slightly adapted version
of <code>VHPI</code>.  Since it is an <code>Ada</code> implementation it is
called <dfn>AVHPI</dfn>. Although being tough, you may interface to <code>AVHPI</code>.

   <p>For using <code>AVHPI</code>, you need the sources of <code>GHDL</code> and to recompile
them (at least the <code>GRT</code> library).  This library is usually compiled with
a <code>No_Run_Time</code> pragma, so that the user does not need to install the
<code>GNAT</code> runtime library.  However, you certainly want to use the usual
runtime library and want to avoid this pragma.  For this, reset the
<var>GRT_PRAGMA_FLAG</var> variable.
<pre class="smallexample">     $ make GRT_PRAGMA_FLAG= grt-all
</pre>
   <p>Since <code>GRT</code> is a self-contained library, you don't want
<code>gnatlink</code> to fetch individual object files (furthermore this
doesn't always work due to tricks used in <code>GRT</code>).  For this,
remove all the object files and make the <samp><span class="file">.ali</span></samp> files read-only.
<pre class="smallexample">     $ rm *.o
     $ chmod -w *.ali
</pre>
   <p>You may then install the sources files and the <samp><span class="file">.ali</span></samp> files.  I have never
tested this step.

   <p>You are now ready to use it.

   <p>For example, here is an example, <samp><span class="file">test_grt.adb</span></samp> which displays the top
level design name.
<pre class="example">     with System; use System;
     with Grt.Avhpi; use Grt.Avhpi;
     with Ada.Text_IO; use Ada.Text_IO;
     with Ghdl_Main;
     
     procedure Test_Grt is
        --  VHPI handle.
        H : VhpiHandleT;
        Status : Integer;
     
        --  Name.
        Name : String (1 .. 64);
        Name_Len : Integer;
     begin
        --  Elaborate and run the design.
        Status := Ghdl_Main (0, Null_Address);
     
        --  Display the status of the simulation.
        Put_Line ("Status is " &amp; Integer'Image (Status));
     
        --  Get the root instance.
        Get_Root_Inst(H);
     
        --  Disp its name using vhpi API.
        Vhpi_Get_Str (VhpiNameP, H, Name, Name_Len);
        Put_Line ("Root instance name: " &amp; Name (1 .. Name_Len));
     end Test_Grt;
</pre>
   <p>First, analyze and bind your design:
<pre class="smallexample">     $ ghdl -a counter.vhdl
     $ ghdl --bind counter
</pre>
   <p>Then build the whole:
<pre class="smallexample">     $ gnatmake test_grt -aL<var>grt_ali_path</var> -aI<var>grt_src_path</var> -largs
      `ghdl --list-link counter`
</pre>
   <p>Finally, run your design:
<pre class="smallexample">     $ ./test_grt
     Status is  0
     Root instance name: counter
</pre>
   <div class="node">
<p><hr>
<a name="GHDL-implementation-of-VITAL"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Flaws-and-bugs-report">Flaws and bugs report</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#GHDL-implementation-of-VHDL">GHDL implementation of VHDL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h2 class="chapter">6 GHDL implementation of VITAL</h2>

<p><a name="index-VITAL-118"></a><a name="index-IEEE-1076_002e4-119"></a><a name="index-g_t1076_002e4-120"></a>This chapter describes how VITAL is implemented in GHDL.  Support of VITAL is
really in a preliminary stage.  Do not expect too much of it as now.

<ul class="menu">
<li><a accesskey="1" href="#VITAL-packages">VITAL packages</a>
<li><a accesskey="2" href="#VHDL-restrictions-for-VITAL">VHDL restrictions for VITAL</a>
<li><a accesskey="3" href="#Backannotation">Backannotation</a>
<li><a accesskey="4" href="#Negative-constraint-calculation">Negative constraint calculation</a>
</ul>

<div class="node">
<p><hr>
<a name="VITAL-packages"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#VHDL-restrictions-for-VITAL">VHDL restrictions for VITAL</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">6.1 VITAL packages</h3>

<p>The VITAL standard or IEEE 1076.4 was first published in 1995, and revised in
2000.

   <p>The version of the VITAL packages depends on the VHDL standard.  VITAL
1995 packages are used with the VHDL 1987 standard, while VITAL 2000
packages are used with other standards.  This choice is based on the
requirements of VITAL: VITAL 1995 requires the models follow the VHDL
1987 standard, while VITAL 2000 requires the models follow VHDL 1993.

   <p>The VITAL 2000 packages were slightly modified so that they conform to
the VHDL 1993 standard (a few functions are made pure and a few one
impure).

<div class="node">
<p><hr>
<a name="VHDL-restrictions-for-VITAL"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Backannotation">Backannotation</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#VITAL-packages">VITAL packages</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">6.2 VHDL restrictions for VITAL</h3>

<p>The VITAL standard (partially) implemented is the IEEE 1076.4 standard
published in 1995.

   <p>This standard defines restriction of the VHDL language usage on VITAL
model.  A <dfn>VITAL model</dfn> is a design unit (entity or architecture)
decorated by the <code>VITAL_Level0</code> or <code>VITAL_Level1</code> attribute. 
These attributes are defined in the <code>ieee.VITAL_Timing</code> package.

   <p>Currently, only VITAL level 0 checks are implemented.  VITAL level 1 models
can be analyzed, but GHDL doesn't check they comply with the VITAL standard.

   <p>Moreover, GHDL doesn't check (yet) that timing generics are not read inside
a VITAL level 0 model prior the VITAL annotation.

   <p>The analysis of a non-conformant VITAL model fails.  You can disable the
checks of VITAL restrictions with the <samp><span class="option">--no-vital-checks</span></samp>.  Even when
restrictions are not checked, SDF annotation can be performed.

<div class="node">
<p><hr>
<a name="Backannotation"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Negative-constraint-calculation">Negative constraint calculation</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#VHDL-restrictions-for-VITAL">VHDL restrictions for VITAL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">6.3 Backannotation</h3>

<p><a name="index-SDF-121"></a><dfn>Backannotation</dfn> is the process of setting VITAL generics with timing
information provided by an external files.

   <p>The external files must be SDF (Standard Delay Format) files.  GHDL
supports a tiny subset of SDF version 2.1, other version number can be
used, provided no features added by the next version are used.

   <p>Hierarchical instance names are not supported. However you can use a list of
instances.  If there is no instance, the top entity will be annotated and
the celltype must be the name of the top entity.  If there is at least one
instance, the last instance name must be a component instantiation label, and
the celltype must be the name of the component declaration instantiated.

   <p>Instances being annotated are not required to be VITAL compliant.  However
generics being annotated must follow rules of VITAL (e.g., type must be a
suitable vital delay type).

   <p>Currently, only timing constraints applying on a timing generic of type
<code>VitalDelayType01</code> has been implemented.  This SDF annotator is
just a proof of concept.  Features will be added with the following GHDL
release.

<div class="node">
<p><hr>
<a name="Negative-constraint-calculation"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Backannotation">Backannotation</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">6.4 Negative constraint calculation</h3>

<p>Negative constraint delay adjustment are necessary to handle negative
constraint such as a negative setup time.  This step is defined in the VITAL
standard and should occur after backannotation.

   <p>GHDL does not do negative constraint calculation.  It fails to handle models
with negative constraint.  I hope to be able to add this phase soon.

<div class="node">
<p><hr>
<a name="Flaws-and-bugs-report"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Copyrights">Copyrights</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h2 class="chapter">7 Flaws and bugs report</h2>

<p>The current version of GHDL is really a beta version.  Some features of
VHDL have not been implemented or are only partially implemented.  Besides,
GHDL has not been extensively tested yet.

<ul class="menu">
<li><a accesskey="1" href="#Deficiencies">Deficiencies</a>
<li><a accesskey="2" href="#Reporting-bugs">Reporting bugs</a>
<li><a accesskey="3" href="#Future-improvements">Future improvements</a>
</ul>

<div class="node">
<p><hr>
<a name="Deficiencies"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Reporting-bugs">Reporting bugs</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Flaws-and-bugs-report">Flaws and bugs report</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Flaws-and-bugs-report">Flaws and bugs report</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">7.1 Deficiencies</h3>

<p>Here is the non-exhaustive list of flaws:

     <ul>
<li>So far, <code>GHDL</code> has been compiled and tested only on &lsquo;<samp><span class="samp">i386-linux</span></samp>&rsquo; systems. 
<li>Overflow detection is not yet implemented. 
<li>Some constraint checks are missing. 
<li>VHDL-93 is not completely implemented. 
<li>There are no checks for elaboration order. 
<li>This list is not exhaustive. 
<li><small class="dots">...</small>
</ul>

<div class="node">
<p><hr>
<a name="Reporting-bugs"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Future-improvements">Future improvements</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Deficiencies">Deficiencies</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Flaws-and-bugs-report">Flaws and bugs report</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">7.2 Reporting bugs</h3>

<p>In order to improve GHDL, we welcome bugs report and suggestions for
any aspect of GHDL.  Please use the bug tracker on
&lt;<code>http://gna.org/projects/ghdl</code>&gt;.  You may also send an
email to <a href="mailto:ghdl@free.fr">ghdl@free.fr</a>.

   <p>If the compiler crashes, this is a bug.  Reliable tools never crash.

   <p>If your compiled VHDL executable crashes, this may be a bug at
runtime or the code produced may be wrong.  However, since VHDL
has a notion of pointers, an erroneous VHDL program (using invalid
pointers for example) may crash.

   <p>If the compiler emits an error message for a perfectly valid input or
does not emit an error message for an invalid input, this may be a bug. 
Please send the input file and what you expected.  If you know the LRM
well enough, please specify the paragraph which has not been well
implemented.  If you don't know the LRM, maybe your bug report will be
rejected simply because there is no bug.  In the latter case, it may be
difficult to discuss the issue; and comparisons with other VHDL tools
is not a very strong argument.

   <p>If a compiler message is not clear enough for you, please tell me.  The
error messages can be improved, but I have not enough experience with
them.

   <p>If you have found a mistake in the manual, please send a comment.  If
you have not understood some parts of this manual, please tell me. 
English is not my mother tongue, so this manual may not be well-written. 
Again, rewriting part of it is a good way to improve it.

   <p>If you send a <code>VHDL</code> file producing a bug, it is a good idea to try
to make it as short as possible.  It is also a good idea to make it
looking like a test: write a comment which explains whether the file
should compile, and if yes, whether or not it should run successfully. 
In the latter case, an assert statement should finish the test; the
severity level note indicates success, while a severity level failure
indicates failure.

   <p>For bug reports, please include enough information for the maintainers to
reproduce the problem. This includes:

     <ul>
<li>the version of <code>GHDL</code> (you can get it with &lsquo;<samp><span class="samp">ghdl --version</span></samp>&rsquo;). 
<li>the operating system
<li>whether you have built <code>GHDL</code> from sources or used the binary
distribution. 
<li>the content of the input files
<li>a description of the problem and samples of any erroneous input
<li>anything else that you think would be helpful. 
</ul>

<div class="node">
<p><hr>
<a name="Future-improvements"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Reporting-bugs">Reporting bugs</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Flaws-and-bugs-report">Flaws and bugs report</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h3 class="section">7.3 Future improvements</h3>

<p>I have several axes for <code>GHDL</code> improvements:
     <ul>
<li>Documentation. 
<li>Better diagnostics messages (warning and error). 
<li>Full support of VHDL-87 and VHDL-93. 
<li>Support of VHDL-02. 
<li>Optimization (simulation speed). 
<li>Graphical tools (to see waves and to debug)
<li>Style checks
<li>VITAL acceleration
</ul>

<!-- And without any order: -->
<!-- VHPI -->
<!-- FOREIGN -->
<!-- AMS -->
<!-- verilog -->
<div class="node">
<p><hr>
<a name="Copyrights"></a>
Next:&nbsp;<a rel="next" accesskey="n" href="#Index">Index</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Flaws-and-bugs-report">Flaws and bugs report</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<!-- node-name,  next,  previous,  up -->
<h2 class="chapter">8 Copyrights</h2>

<p>The GHDL front-end, the &lsquo;<samp><span class="samp">std.textio</span></samp>&rsquo; package and the runtime
library (grt) are copyrighted Tristan Gingold, come with <em>absolutely
no warranty</em>, and are distributed under the conditions of the General
Public License.

   <p>The &lsquo;<samp><span class="samp">ieee.numeric_bit</span></samp>&rsquo; and &lsquo;<samp><span class="samp">ieee.numeric_std</span></samp>&rsquo; packages are
copyrighted by the IEEE.  The source files may be distributed without
change, except as permitted by the standard. 
<!-- FIXME: this sounds strange -->
This source file may not be
sold or distributed for profit.  See the source file and the IEEE 1076.3
standard for more information.

   <p>The &lsquo;<samp><span class="samp">ieee.std_logic_1164</span></samp>&rsquo; package is copyrighted by the IEEE.  See
source file and the IEEE 1164 standard for more information.

   <p>The &lsquo;<samp><span class="samp">ieee.VITAL_Primitives</span></samp>&rsquo;, &lsquo;<samp><span class="samp">ieee.VITAL_Timing</span></samp>&rsquo; and
&lsquo;<samp><span class="samp">ieee.VITAL_Memory</span></samp>&rsquo; packages are copyrighted by IEEE.  See source
file and the IEEE 1076.4 standards for more information.

   <p>The &lsquo;<samp><span class="samp">ieee.Math_Real</span></samp>&rsquo; and &lsquo;<samp><span class="samp">ieee.Math_Complex</span></samp>&rsquo; packages are
copyrighted by IEEE.  These are draft versions which may used and distributed
without restriction.  These packages cannot be sold or distributed for profit. 
See source files for more information.

   <p>The packages &lsquo;<samp><span class="samp">std_logic_arith</span></samp>&rsquo;, <!-- @samp{std_logic_misc}, -->
&lsquo;<samp><span class="samp">std_logic_signed</span></samp>&rsquo;, &lsquo;<samp><span class="samp">std_logic_unsigned</span></samp>&rsquo; and
&lsquo;<samp><span class="samp">std_logic_textio</span></samp>&rsquo; contained in the &lsquo;<samp><span class="samp">synopsys</span></samp>&rsquo; directory are
copyrighted by Synopsys, Inc.  The source files may be used and
distributed without restriction provided that the copyright statements
are not removed from the files and that any derivative work contains the
copyright notice.  See the source files for more information.

   <p>The package &lsquo;<samp><span class="samp">std_logic_arith</span></samp>&rsquo; contained in the &lsquo;<samp><span class="samp">mentor</span></samp>&rsquo;
directory is copyrighted by Mentor Graphics.  The source files may be
distributed in whole without restriction provided that the copyright
statement is not removed from the file and that any derivative work
contains this copyright notice.  See the source files for more information.

   <p>As a consequence of the runtime copyright, you may not be allowed to
distribute an executable produced by <code>GHDL</code> without the VHDL
sources.  To my mind, this is not a real restriction, since there is no
points in distributing VHDL executable.  Please, send a comment
(see <a href="#Reporting-bugs">Reporting bugs</a>) if you don't like this policy.

<div class="node">
<p><hr>
<a name="Index"></a>
Previous:&nbsp;<a rel="previous" accesskey="p" href="#Copyrights">Copyrights</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="#Top">Top</a>

</div>

<h2 class="unnumbered">Index</h2>

<ul class="index-cp" compact>
<li><a href="#index-g_t_0040option_007b_002d_002dassert_002dlevel_007d-option-79"><samp><span class="option">--assert-level</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dbind_007d-command-10"><samp><span class="option">--bind</span></samp> command</a>: <a href="#Bind-command">Bind command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dchop_007d-command-67"><samp><span class="option">--chop</span></samp> command</a>: <a href="#Chop-command">Chop command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dclean_007d-command-58"><samp><span class="option">--clean</span></samp> command</a>: <a href="#Clean-command">Clean command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dcopy_007d-command-62"><samp><span class="option">--copy</span></samp> command</a>: <a href="#Copy-command">Copy command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002ddisp_002dstandard_007d-command-73"><samp><span class="option">--disp-standard</span></samp> command</a>: <a href="#Disp-standard-command">Disp standard command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002ddisp_002dtime_007d-option-83"><samp><span class="option">--disp-time</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002ddisp_002dtree_007d-option-85"><samp><span class="option">--disp-tree</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002ddispconfig_007d-command-71"><samp><span class="option">--dispconfig</span></samp> command</a>: <a href="#Dispconfig-command">Dispconfig command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002delab_002drun_007d-command-8"><samp><span class="option">--elab-run</span></samp> command</a>: <a href="#Elaborate-and-run-command">Elaborate and run command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dgen_002dmakefile_007d-command-54"><samp><span class="option">--gen-makefile</span></samp> command</a>: <a href="#Generate-Makefile-command">Generate Makefile command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dGHLD1_007d-switch-36"><samp><span class="option">--GHLD1</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dhelp_007d-command-70"><samp><span class="option">--help</span></samp> command</a>: <a href="#Help-command">Help command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dieee_007d-switch-26"><samp><span class="option">--ieee</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dieee_002dasserts_007d-option-80"><samp><span class="option">--ieee-asserts</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dlines_007d-command-68"><samp><span class="option">--lines</span></samp> command</a>: <a href="#Lines-command">Lines command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dlink_007d-command-12"><samp><span class="option">--link</span></samp> command</a>: <a href="#Link-command">Link command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dlist_002dlink_007d-command-13"><samp><span class="option">--list-link</span></samp> command</a>: <a href="#List-link-command">List link command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dno_002drun_007d-option-87"><samp><span class="option">--no-run</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dno_002dvital_002dchecks_007d-switch-32"><samp><span class="option">--no-vital-checks</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dpp_002dhtml_007d-command-63"><samp><span class="option">--pp-html</span></samp> command</a>: <a href="#Pretty-print-command">Pretty print command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dPREFIX_007d-switch-35"><samp><span class="option">--PREFIX</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dremove_007d-command-60"><samp><span class="option">--remove</span></samp> command</a>: <a href="#Remove-command">Remove command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dsdf_007d-option-94"><samp><span class="option">--sdf</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dstack_002dmax_002dsize_007d-option-95"><samp><span class="option">--stack-max-size</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dstack_002dsize_007d-option-96"><samp><span class="option">--stack-size</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dstd_007d-switch-25"><samp><span class="option">--std</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dstop_002ddelta_007d-option-82"><samp><span class="option">--stop-delta</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dstop_002dtime_007d-option-81"><samp><span class="option">--stop-time</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dsyn_002dbinding_007d-switch-34"><samp><span class="option">--syn-binding</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dvcd_007d-option-88"><samp><span class="option">--vcd</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dvcdgz_007d-option-89"><samp><span class="option">--vcdgz</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dversion_007d-command-75"><samp><span class="option">--version</span></samp> command</a>: <a href="#Version-command">Version command</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dvital_002dchecks_007d-switch-33"><samp><span class="option">--vital-checks</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002dbinding_007d-switch-42"><samp><span class="option">--warn-binding</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002dbody_007d-switch-46"><samp><span class="option">--warn-body</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002ddefault_002dbinding_007d-switch-41"><samp><span class="option">--warn-default-binding</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002ddelayed_002dchecks_007d-switch-45"><samp><span class="option">--warn-delayed-checks</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002derror_007d-switch-49"><samp><span class="option">--warn-error</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002dlibrary_007d-switch-43"><samp><span class="option">--warn-library</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002dreserved_007d-switch-40"><samp><span class="option">--warn-reserved</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002dspecs_007d-switch-47"><samp><span class="option">--warn-specs</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002dunused_007d-switch-48"><samp><span class="option">--warn-unused</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwarn_002dvital_002dgeneric_007d-switch-44"><samp><span class="option">--warn-vital-generic</span></samp> switch</a>: <a href="#GHDL-warnings">GHDL warnings</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwave_007d-option-93"><samp><span class="option">--wave</span></samp> option</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dwork_007d-switch-22"><samp><span class="option">--work</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002d_002dworkdir_007d-switch-24"><samp><span class="option">--workdir</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002da_007d-command-2"><samp><span class="option">-a</span></samp> command</a>: <a href="#Analysis-command">Analysis command</a></li>
<li><a href="#index-g_t_0040option_007b_002dc_007d-command-17"><samp><span class="option">-c</span></samp> command</a>: <a href="#Analyze-and-elaborate-command">Analyze and elaborate command</a></li>
<li><a href="#index-g_t_0040option_007b_002dd_007d-command-56"><samp><span class="option">-d</span></samp> command</a>: <a href="#Directory-command">Directory command</a></li>
<li><a href="#index-g_t_0040option_007b_002de_007d-command-4"><samp><span class="option">-e</span></samp> command</a>: <a href="#Elaboration-command">Elaboration command</a></li>
<li><a href="#index-g_t_0040option_007b_002df_007d-command-66"><samp><span class="option">-f</span></samp> command</a>: <a href="#Find-command">Find command</a></li>
<li><a href="#index-g_t_0040option_007b_002dfexplicit_007d-switch-31"><samp><span class="option">-fexplicit</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002dh_007d-command-69"><samp><span class="option">-h</span></samp> command</a>: <a href="#Help-command">Help command</a></li>
<li><a href="#index-g_t_0040option_007b_002di_007d-command-51"><samp><span class="option">-i</span></samp> command</a>: <a href="#Import-command">Import command</a></li>
<li><a href="#index-g_t_0040option_007b_002dm_007d-command-53"><samp><span class="option">-m</span></samp> command</a>: <a href="#Make-command">Make command</a></li>
<li><a href="#index-g_t_0040option_007b_002dP_007d-switch-30"><samp><span class="option">-P</span></samp> switch</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040option_007b_002dr_007d-command-6"><samp><span class="option">-r</span></samp> command</a>: <a href="#Run-command">Run command</a></li>
<li><a href="#index-g_t_0040option_007b_002ds_007d-command-15"><samp><span class="option">-s</span></samp> command</a>: <a href="#Check-syntax-command">Check syntax command</a></li>
<li><a href="#index-g_t_0040option_007b_002dW_007d-switch-37"><samp><span class="option">-W</span></samp> switch</a>: <a href="#Passing-options-to-other-programs">Passing options to other programs</a></li>
<li><a href="#index-g_t_0040option_007b_002dWa_007d-switch-38"><samp><span class="option">-Wa</span></samp> switch</a>: <a href="#Passing-options-to-other-programs">Passing options to other programs</a></li>
<li><a href="#index-g_t_0040option_007b_002dWl_007d-switch-39"><samp><span class="option">-Wl</span></samp> switch</a>: <a href="#Passing-options-to-other-programs">Passing options to other programs</a></li>
<li><a href="#index-g_t1076-102">1076</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-g_t1076_002e3-21">1076.3</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t1076_002e4-120">1076.4</a>: <a href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a></li>
<li><a href="#index-g_t1076a-103">1076a</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-g_t1164-19">1164</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-g_t_0040code_007b_005f_005fghdl_005ffatal_007d-98"><code>__ghdl_fatal</code></a>: <a href="#Debugging-VHDL-programs">Debugging VHDL programs</a></li>
<li><a href="#index-analysis-1">analysis</a>: <a href="#Analysis-command">Analysis command</a></li>
<li><a href="#index-Analyze-and-elaborate-command-16">Analyze and elaborate command</a>: <a href="#Analyze-and-elaborate-command">Analyze and elaborate command</a></li>
<li><a href="#index-binding-9">binding</a>: <a href="#Bind-command">Bind command</a></li>
<li><a href="#index-checking-syntax-14">checking syntax</a>: <a href="#Check-syntax-command">Check syntax command</a></li>
<li><a href="#index-cleaning-57">cleaning</a>: <a href="#Clean-command">Clean command</a></li>
<li><a href="#index-cleaning-all-59">cleaning all</a>: <a href="#Remove-command">Remove command</a></li>
<li><a href="#index-copying-library-61">copying library</a>: <a href="#Copy-command">Copy command</a></li>
<li><a href="#index-debugging-97">debugging</a>: <a href="#Debugging-VHDL-programs">Debugging VHDL programs</a></li>
<li><a href="#index-display-configuration-72">display configuration</a>: <a href="#Dispconfig-command">Dispconfig command</a></li>
<li><a href="#index-display-design-hierarchy-86">display design hierarchy</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-display-_0040samp_007bstd_002estandard_007d-74">display &lsquo;<samp><span class="samp">std.standard</span></samp>&rsquo;</a>: <a href="#Disp-standard-command">Disp standard command</a></li>
<li><a href="#index-display-time-84">display time</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-displaying-library-55">displaying library</a>: <a href="#Directory-command">Directory command</a></li>
<li><a href="#index-dump-of-signals-92">dump of signals</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-elaborate-and-run-7">elaborate and run</a>: <a href="#Elaborate-and-run-command">Elaborate and run command</a></li>
<li><a href="#index-elaboration-3">elaboration</a>: <a href="#Elaboration-command">Elaboration command</a></li>
<li><a href="#index-file-format-109">file format</a>: <a href="#VHDL-files-format">VHDL files format</a></li>
<li><a href="#index-foreign-115">foreign</a>: <a href="#Interfacing-to-other-languages">Interfacing to other languages</a></li>
<li><a href="#index-IEEE-1076-100">IEEE 1076</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-IEEE-1076_002e3-20">IEEE 1076.3</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-IEEE-1076_002e4-119">IEEE 1076.4</a>: <a href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a></li>
<li><a href="#index-IEEE-1076a-101">IEEE 1076a</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-IEEE-1164-18">IEEE 1164</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-ieee-library-27">ieee library</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-importing-files-50">importing files</a>: <a href="#Import-command">Import command</a></li>
<li><a href="#index-interfacing-113">interfacing</a>: <a href="#Interfacing-to-other-languages">Interfacing to other languages</a></li>
<li><a href="#index-linking-11">linking</a>: <a href="#Link-command">Link command</a></li>
<li><a href="#index-logical-name-110">logical name</a>: <a href="#VHDL-files-format">VHDL files format</a></li>
<li><a href="#index-make-52">make</a>: <a href="#Make-command">Make command</a></li>
<li><a href="#index-math_005fcomplex-112">math_complex</a>: <a href="#Using-ieee_002emath_005freal-or-ieee_002emath_005fcomplex">Using ieee.math_real or ieee.math_complex</a></li>
<li><a href="#index-Math_005fComplex-78">Math_Complex</a>: <a href="#IEEE-math-packages">IEEE math packages</a></li>
<li><a href="#index-math_005freal-111">math_real</a>: <a href="#Using-ieee_002emath_005freal-or-ieee_002emath_005fcomplex">Using ieee.math_real or ieee.math_complex</a></li>
<li><a href="#index-Math_005fReal-77">Math_Real</a>: <a href="#IEEE-math-packages">IEEE math packages</a></li>
<li><a href="#index-mentor-library-29">mentor library</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-other-languages-114">other languages</a>: <a href="#Interfacing-to-other-languages">Interfacing to other languages</a></li>
<li><a href="#index-pretty-printing-64">pretty printing</a>: <a href="#Pretty-print-command">Pretty print command</a></li>
<li><a href="#index-run-5">run</a>: <a href="#Run-command">Run command</a></li>
<li><a href="#index-SDF-121">SDF</a>: <a href="#Backannotation">Backannotation</a></li>
<li><a href="#index-synopsys-library-28">synopsys library</a>: <a href="#GHDL-options">GHDL options</a></li>
<li><a href="#index-v00-107">v00</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-v02-108">v02</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-v87-104">v87</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-v93-105">v93</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-v93c-106">v93c</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-value-change-dump-91">value change dump</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-vcd-90">vcd</a>: <a href="#Simulation-options">Simulation options</a></li>
<li><a href="#index-version-76">version</a>: <a href="#Version-command">Version command</a></li>
<li><a href="#index-VHDL-standards-99">VHDL standards</a>: <a href="#VHDL-standards">VHDL standards</a></li>
<li><a href="#index-vhdl-to-html-65">vhdl to html</a>: <a href="#Pretty-print-command">Pretty print command</a></li>
<li><a href="#index-VHPI-116">VHPI</a>: <a href="#Interfacing-to-other-languages">Interfacing to other languages</a></li>
<li><a href="#index-VHPIDIRECT-117">VHPIDIRECT</a>: <a href="#Interfacing-to-other-languages">Interfacing to other languages</a></li>
<li><a href="#index-VITAL-118">VITAL</a>: <a href="#GHDL-implementation-of-VITAL">GHDL implementation of VITAL</a></li>
<li><a href="#index-WORK-library-23">WORK library</a>: <a href="#GHDL-options">GHDL options</a></li>
   </ul></body></html>
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