The Windows 0.29.1 GHDL build errors at compile time when
an attribute is placed on a signal for which an alias has 
previously been created.

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Code snippet from attached <alias_bug.vhd> example:

   signal processor_address : std_logic_vector(15 downto 0);

   alias  address_ms       : std_logic_vector(3 downto 0)   is   processor_address(15 downto 12);

   attribute keep : boolean;
   attribute keep of processor_address: signal is TRUE;

Resulting error message:

 .\alias_bug.vhd:35:13: alias "address_ms" does not denote the entire object

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Workaround:

 Moving the alias _after_ the attribute causes the error to go away.

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alias_bug.zip contents : 

 alias_bug.txt              this file
 alias_bug.vhd              test program to demonstrate alias bug
 ghdc.bat                   batch file to invoke compiler