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From: "rjones at redhat dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/52560] New: if (r == -1) causes 'assuming signed overflow does not occur when simplifying conditional to constant' Date: Mon, 12 Mar 2012 11:19:00 -0000 [thread overview] Message-ID: <bug-52560-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52560 Bug #: 52560 Summary: if (r == -1) causes 'assuming signed overflow does not occur when simplifying conditional to constant' Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned@gcc.gnu.org ReportedBy: rjones@redhat.com Here is the reproducer: wget 'http://oirase.annexia.org/strict-overflow-warning.i.xz' unxz strict-overflow-warning.i.xz gcc -std=gnu99 -O2 -Wstrict-overflow -c strict-overflow-warning.i The warning is: inspect_fs_unix.c: In function ‘check_fstab’: inspect_fs_unix.c:1075:6: warning: assuming signed overflow does not occur when simplifying conditional to constant [-Wstrict-overflow] However the code doesn't look like anything should be simplified, or a warning: n_app_md_devices = map_app_md_devices (g, &app_map); if (n_app_md_devices == -1) goto error; where map_app_md_devices is a function that returns an int: static int map_app_md_devices (guestfs_h *g, Hash_table **map); and n_app_md_devices is also an int. I've tried this on several versions of gcc: gcc (GCC) 4.7.0 20120308 (Red Hat 4.7.0-0.19) Copyright (C) 2012 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. (for further build info, go to: http://koji.fedoraproject.org/koji/buildinfo?buildID=305760 and click 'build logs') Same thing with this gcc from Ubuntu 11.10: $ gcc --version gcc (Ubuntu/Linaro 4.6.1-9ubuntu3) 4.6.1 Copyright (C) 2011 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. We think this first started happening in gcc 4.5.1.
next reply other threads:[~2012-03-12 11:19 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-03-12 11:19 rjones at redhat dot com [this message] 2012-03-12 12:30 ` [Bug c/52560] " jim at meyering dot net 2012-03-12 13:23 ` [Bug tree-optimization/52560] " rguenth at gcc dot gnu.org 2012-03-12 16:31 ` rjones at redhat dot com
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