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[patch] Fix PR C++/82872
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 21 Dec 2017 16:51:40 +0100
- Subject: [patch] Fix PR C++/82872
- Authentication-results: sourceware.org; auth=none
Hi,
this is an ICE in the C++ FE on an offsetof construct with __PTRDIFF_MAX__ and
it happens only with this specific index:
In file included from pr82872.c:4:
pr82872.c: In function 'size_t foo()':
pr82872.c:10:10: internal compiler error: in ignore_overflows, at cp/cvt.c:583
return offsetof (struct S, a[__PTRDIFF_MAX__]);
^~~~~~~~
0x65ef7f ignore_overflows
/home/eric/svn/gcc/gcc/cp/cvt.c:583
0x661bcc ocp_convert(tree_node*, tree_node*, int, int, int)
/home/eric/svn/gcc/gcc/cp/cvt.c:817
0x6636e0 convert(tree_node*, tree_node*)
/home/eric/svn/gcc/gcc/cp/cvt.c:1580
0x882b62 fold_offsetof(tree_node*)
/home/eric/svn/gcc/gcc/c-family/c-common.c:6282
0x801c0c finish_offsetof(tree_node*, tree_node*, unsigned int)
/home/eric/svn/gcc/gcc/cp/semantics.c:4041
0x74596b cp_parser_builtin_offsetof
/home/eric/svn/gcc/gcc/cp/parser.c:9828
The C++ FE is quite picky about constant integer overflow during conversion
operations and checks that they can only _introduce_ overflows and never make
them disappear, the latter case occuring here in convert_to_integer_1.
Tested on x86_64-suse-linux, OK for the mainline?
2017-12-21 Eric Botcazou <ebotcazou@adacore.com>
PR C++/82872
* convert.c (convert_to_integer_1) <POINTER_TYPE>: Do not return
the shared zero if the input has overflowed.
2017-12-21 Eric Botcazou <ebotcazou@adacore.com>
* c-c++-common/pr82872.c: New test.
--
Eric Botcazou/* PR c++/82872 */
/* { dg-do compile } */
#include <stddef.h>
struct S { int i, a[1]; };
size_t foo (void)
{
return offsetof (struct S, a[__PTRDIFF_MAX__]);
}
Index: convert.c
===================================================================
--- convert.c (revision 255850)
+++ convert.c (working copy)
@@ -671,7 +671,7 @@ convert_to_integer_1 (tree type, tree ex
{
case POINTER_TYPE:
case REFERENCE_TYPE:
- if (integer_zerop (expr))
+ if (integer_zerop (expr) && !TREE_OVERFLOW (expr))
return build_int_cst (type, 0);
/* Convert to an unsigned integer of the correct width first, and from