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: [email protected]
ReportedBy: [email protected]
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.
