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[Ada] Do not remove side-effects in an others_clause with function calls


An aggregate can be handled by the backend if it consists of static
constants of an elementary type, or null. If a component is a type
conversion we must preanalyze and resolve it to determine whether the
ultimate value is in one of these categories.  Previously we did a full
analysis and resolution of the expression for the component, which could
lead to a removal of side-effects, which is semantically incorrect if
the expression includes functions with side-effects (e.g. a call to a
random generator).

Tested on x86_64-pc-linux-gnu, committed on trunk

2019-08-13  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_aggr.adb (Aggr_Assignment_OK_For_Backend):  Preanalyze
	expression, rather do a full analysis, to prevent unwanted
	removal of side effects which mask the intent of the expression.

gcc/testsuite/

	* gnat.dg/aggr27.adb: New testcase.
--- gcc/ada/exp_aggr.adb
+++ gcc/ada/exp_aggr.adb
@@ -5321,6 +5321,16 @@ package body Exp_Aggr is
             return False;
          end if;
 
+         --  If the expression has side effects (e.g. contains calls with
+         --  potential side effects) reject as well. We only preanalyze the
+         --  expression to prevent the removal of intended side effects.
+
+         Preanalyze_And_Resolve (Expr, Ctyp);
+
+         if not Side_Effect_Free (Expr) then
+            return False;
+         end if;
+
          --  The expression needs to be analyzed if True is returned
 
          Analyze_And_Resolve (Expr, Ctyp);

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/aggr27.adb
@@ -0,0 +1,26 @@
+--  { dg-do run }
+--  { dg-options "-gnatws -gnata" }
+
+with GNAT.Random_Numbers;
+
+procedure Aggr27 is
+
+   Gen: GNAT.Random_Numbers.Generator;
+
+   function Random return Long_Long_Integer is
+      Rand : Integer := GNAT.Random_Numbers.Random(Gen);
+   begin
+      return Long_Long_Integer(Rand);
+   end Random;
+
+   type Values is range 1 .. 4;
+
+   Seq_LLI : array (Values) of Long_Long_Integer := (others => Random);
+   Seq_I   : array (Values) of Integer           := (others => Integer(Random));
+
+begin
+   --  Verify that there is at least two  different entries in each.
+
+   pragma Assert (For some E of Seq_LLI => E /= Seq_LLI (Values'First));
+   pragma Assert (For some E of Seq_I => E /= Seq_I (Values'First));
+end Aggr27;


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