From faef2db5bbe258f9ac4f9e357f8db878903ca528 Mon Sep 17 00:00:00 2001
From: Tristan Gingold <tgingold@free.fr>
Date: Tue, 21 Apr 2020 07:41:09 +0200
Subject: synth-stmts: add a limit to the number of iterations.  Fix #1242

---
 src/synth/synth-flags.ads |  3 +++
 src/synth/synth-stmts.adb | 11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/src/synth/synth-flags.ads b/src/synth/synth-flags.ads
index 4f9badd1d..3fc9303c5 100644
--- a/src/synth/synth-flags.ads
+++ b/src/synth/synth-flags.ads
@@ -57,4 +57,7 @@ package Synth.Flags is
 
    --  True to start debugger on error.
    Flag_Debug_Enable : Boolean := True;
+
+   --  Maximum number of iterations for (while)/loop.  0 means unlimited.
+   Flag_Max_Loop : Natural := 1000;
 end Synth.Flags;
diff --git a/src/synth/synth-stmts.adb b/src/synth/synth-stmts.adb
index efece924c..61833ab58 100644
--- a/src/synth/synth-stmts.adb
+++ b/src/synth/synth-stmts.adb
@@ -2328,6 +2328,7 @@ package body Synth.Stmts is
       Cond : constant Node := Get_Condition (Stmt);
       Val : Valtyp;
       Lc : aliased Loop_Context (Mode_Dynamic);
+      Iter_Nbr : Natural;
    begin
       Lc := (Mode => Mode_Dynamic,
              Prev_Loop => C.Cur_Loop,
@@ -2339,6 +2340,8 @@ package body Synth.Stmts is
              Wire_Mark => No_Wire_Id);
       C.Cur_Loop := Lc'Unrestricted_Access;
 
+      Iter_Nbr := 0;
+
       Loop_Control_Init (C, Stmt);
 
       loop
@@ -2371,6 +2374,14 @@ package body Synth.Stmts is
          then
             exit;
          end if;
+
+         Iter_Nbr := Iter_Nbr + 1;
+         if Iter_Nbr > Flags.Flag_Max_Loop and Flags.Flag_Max_Loop /= 0 then
+            Error_Msg_Synth
+              (+Stmt, "maximum number of iterations (%v) reached",
+               +Uns32 (Flags.Flag_Max_Loop));
+            exit;
+         end if;
       end loop;
       Loop_Control_Finish (C);
 
-- 
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