| Summary: | folding causes strict aliasing violation | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Richard Biener <rguenth> |
| Component: | middle-end | Assignee: | Richard Biener <rguenth> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | gcc-bugs |
| Priority: | P3 | Keywords: | alias, wrong-code |
| Version: | 4.5.0 | ||
| Target Milestone: | --- | ||
| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | 2009-09-09 12:16:29 | |
| Bug Depends on: | |||
| Bug Blocks: | 41316 | ||
4.4 rightfully complains: t.i: In function ‘main’: t.i:16: warning: dereferencing pointer ‘a.0’ does break strict-aliasing rules t.i:23: note: initialized from here Mine. Fixed. Subject: Bug 41317 Author: rguenth Date: Wed Sep 9 14:35:51 2009 New Revision: 151559 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=151559 Log: 2009-09-09 Richard Guenther <rguenther@suse.de> PR middle-end/41317 * tree-ssa-ccp.c (maybe_fold_offset_to_component_ref): Remove code dealing with plain pointer bases. (maybe_fold_offset_to_reference): Likewise. (maybe_fold_stmt_addition): Adjust. * gcc.c-torture/execute/pr41317.c: New testcase. * gcc.dg/tree-ssa/forwprop-11.c: XFAIL. * gcc.dg/tree-ssa/forwprop-12.c: Likewise. Added: trunk/gcc/testsuite/gcc.c-torture/execute/pr41317.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gcc.dg/tree-ssa/forwprop-11.c trunk/gcc/testsuite/gcc.dg/tree-ssa/forwprop-12.c trunk/gcc/tree-ssa-ccp.c Subject: Bug 41317 Author: jakub Date: Mon Nov 9 19:38:29 2009 New Revision: 154046 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=154046 Log: PR middle-end/40946 Backport from mainline 2009-09-09 Richard Guenther <rguenther@suse.de> PR middle-end/41317 * tree-ssa-ccp.c (maybe_fold_offset_to_component_ref): Remove code dealing with plain pointer bases. (maybe_fold_offset_to_reference): Likewise. (maybe_fold_stmt_addition): Adjust. PR middle-end/40946 * gcc.dg/pr40946.c: New test. Backport from mainline 2009-09-09 Richard Guenther <rguenther@suse.de> PR middle-end/41317 * gcc.c-torture/execute/pr41317.c: New testcase. Added: branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/execute/pr41317.c branches/gcc-4_4-branch/gcc/testsuite/gcc.dg/pr40946.c Modified: branches/gcc-4_4-branch/gcc/ChangeLog branches/gcc-4_4-branch/gcc/testsuite/ChangeLog branches/gcc-4_4-branch/gcc/tree-ssa-ccp.c |
extern void abort (void); struct A { int i; }; struct B { struct A a; int j; }; static void foo (struct B *p) { ((struct A *)p)->i = 1; } int main() { struct A a; a.i = 0; foo ((struct B *)&a); if (a.i != 1) abort (); return 0; } Folding (struct A *)p to &p->a causes us to see a.i = 0; a.0_1 = (struct B *) &a; a.0_1->a.i = 1; D.2703_2 = a.i; where the store a.0_1->a.i does not alias a.i because of TBAA on the base object (you can't access an object of type A via a pointer to type B). This blocks the fix for PR41316.