Patchwork [C] Don't leak C_MAYBE_CONST_EXPRs into GIMPLE (PR c/59891)

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Submitter Marek Polacek
Date Jan. 22, 2014, 9:04 p.m.
Message ID <20140122210410.GU8907@redhat.com>
Download mbox | patch
Permalink /patch/313418/
State New
Headers show

Comments

Marek Polacek - Jan. 22, 2014, 9:04 p.m.
As mentioned in the PR, C FE leaked C_MAYBE_CONST_EXPR into GIMPLE.
This happened because remove_c_maybe_const_expr doesn't look for
nested C_MAYBE_CONST_EXPRs.  But c_fully_fold will fold these away,
so use that.

Regtested/bootstrapped on x86_64-linux, ok for trunk and 4.8?

Alternatively, we could in if (int_operands) look at op1/op2, and
call c_fully_fold only if C_MAYBE_CONST_EXPR isn't the top level
expression.

2014-01-22  Marek Polacek  <polacek@redhat.com>

	PR c/59891
c/
	* c-typeck.c (build_conditional_expr): Call c_fully_fold instead
	of remove_c_maybe_const_expr on op1 and op2.
testsuite/
	* gcc.dg/torture/pr59891.c: New test.


	Marek
Joseph S. Myers - Jan. 22, 2014, 9:13 p.m.
On Wed, 22 Jan 2014, Marek Polacek wrote:

> 2014-01-22  Marek Polacek  <polacek@redhat.com>
> 
> 	PR c/59891
> c/
> 	* c-typeck.c (build_conditional_expr): Call c_fully_fold instead
> 	of remove_c_maybe_const_expr on op1 and op2.
> testsuite/
> 	* gcc.dg/torture/pr59891.c: New test.

OK.

Patch

--- gcc/c/c-typeck.c.mp3	2014-01-22 18:47:36.812358319 +0100
+++ gcc/c/c-typeck.c	2014-01-22 18:45:10.298692933 +0100
@@ -4708,8 +4708,10 @@  build_conditional_expr (location_t colon
     {
       if (int_operands)
 	{
-	  op1 = remove_c_maybe_const_expr (op1);
-	  op2 = remove_c_maybe_const_expr (op2);
+	  /* Use c_fully_fold here, since C_MAYBE_CONST_EXPR might be
+	     nested inside of the expression.  */
+	  op1 = c_fully_fold (op1, false, NULL);
+	  op2 = c_fully_fold (op2, false, NULL);
 	}
       ret = build3 (COND_EXPR, result_type, ifexp, op1, op2);
       if (int_operands)
--- gcc/testsuite/gcc.dg/torture/pr59891.c.mp3	2014-01-22 19:16:34.000000000 +0100
+++ gcc/testsuite/gcc.dg/torture/pr59891.c	2014-01-22 19:19:23.996129684 +0100
@@ -0,0 +1,9 @@ 
+/* PR c/59891 */
+
+unsigned int a;
+
+int
+main ()
+{
+  return (0 ? a : 0) ? : 0 % 0; /* { dg-warning "division by zero" } */
+}