[C++] Explicitly test for TREE_CONSTANT_OVERFLOW in null_ptr_cst_p

Roger Sayle roger@eyesopen.com
Mon Apr 3 16:48:00 GMT 2006


Many thanks to Joseph for pointing out that the g++ front-end's code
probably isn't yet checking for overflow of null pointers constants
explicitly.  Indeed, it's not and there's no test case for this in the
g++ testsuite.  The patch  below adds an explicit TREE_CONSTANT_OVERFLOW
check to null_ptr_cst_p and adds a new g++.dg/conversion test case to
ensure this doesn't break in future.  Whilst I was at it, I decided to
also add another nullptr?.C test case to test the resolution of
PR c++/14644.

The following patch has been tested on i686-pc-linux-gnu with a full
"make bootstrap", including c++, and regression tested with a top-level
"make -k check" with no new failures.

Ok for mainline?



2006-04-03  Roger Sayle  <roger@eyesopen.com>

	* call.c (null_ptr_cst_p): Add explicit TREE_CONSTANT_OVERFLOW check.

	* g++.dg/conversion/nullptr1.C: New test case.
	* g++.dg/conversion/nullptr2.C: Likewise.


Index: call.c
===================================================================
*** call.c	(revision 112522)
--- call.c	(working copy)
*************** null_ptr_cst_p (tree t)
*** 427,433 ****
       (_expr.const_) rvalue of integer type that evaluates to zero.  */
    t = integral_constant_value (t);
    if (t == null_node
!       || (CP_INTEGRAL_TYPE_P (TREE_TYPE (t)) && integer_zerop (t)))
      return true;
    return false;
  }
--- 427,435 ----
       (_expr.const_) rvalue of integer type that evaluates to zero.  */
    t = integral_constant_value (t);
    if (t == null_node
!       || (CP_INTEGRAL_TYPE_P (TREE_TYPE (t))
! 	  && integer_zerop (t)
! 	  && !TREE_CONSTANT_OVERFLOW (t)))
      return true;
    return false;
  }


/* Test for overflow in NULL pointer constant.  */
/* { dg-do compile } */

#include <limits.h>

void *p = 0;

void *q = 0 * (INT_MAX + 1);  // { dg-error "invalid conversion" }



/* Test for enumeration as NULL pointer constant.  */
/* PR c++/14644 */
/* { dg-do compile } */

enum { NULL = 0 };

void *p = 0;

void *q = NULL;  // { dg-error "cannot convert" }


Roger
--



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