[gcc r12-1500] [Ada] ACATS 4.1R-c611a04: Class-wide preconditions in dispatching calls

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:cbb64f6b9ac870176700a2fa723a3b21a53b9b29

commit r12-1500-gcbb64f6b9ac870176700a2fa723a3b21a53b9b29
Author: Javier Miranda <miranda@adacore.com>
Date:   Thu Feb 18 13:47:10 2021 -0500

    [Ada] ACATS 4.1R-c611a04: Class-wide preconditions in dispatching calls
    
    gcc/ada/
    
            * exp_disp.adb (Build_Class_Wide_Check): Ensure that evaluation
            of actuals is side effects free (since the check duplicates
            actuals).

Diff:
---
 gcc/ada/exp_disp.adb | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/gcc/ada/exp_disp.adb b/gcc/ada/exp_disp.adb
index 20a32cd9576..eb6b352bef9 100644
--- a/gcc/ada/exp_disp.adb
+++ b/gcc/ada/exp_disp.adb
@@ -868,6 +868,7 @@ package body Exp_Disp is
 
          Str_Loc : constant String := Build_Location_String (Loc);
 
+         A    : Node_Id;
          Cond : Node_Id;
          Msg  : Node_Id;
          Prec : Node_Id;
@@ -900,6 +901,15 @@ package body Exp_Disp is
                return;
             end if;
 
+            --  Ensure that the evaluation of the actuals will not produce side
+            --  effects (since the check will use a copy of the actuals).
+
+            A := First_Actual (Call_Node);
+            while Present (A) loop
+               Remove_Side_Effects (A);
+               Next_Actual (A);
+            end loop;
+
             --  The expression for the precondition is analyzed within the
             --  generated pragma. The message text is the last parameter of
             --  the generated pragma, indicating source of precondition.