https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66625
Bug ID: 66625
Summary: xorg-server (Ext/Xinerama) fails to build with -O3
optimizations
Product: gcc
Version: 5.1.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: peter.ganzhorn at gmail dot com
Target Milestone: ---
GCC 5.1.0 fails to build xorg-server with the -O3 option with the following
output:
xvdisp.c: In function ‘XineramifyXv’:
xvdisp.c:1783:37: error: array subscript is above array bounds
[-Werror=array-bounds]
if (MatchingAdaptors[k] && (MatchingAdaptors[k]->nPorts > j))
^
xvdisp.c:1784:31: error: array subscript is above array bounds
[-Werror=array-bounds]
port->info[k].id = MatchingAdaptors[k]->base_id + j;
^
xvdisp.c:1786:31: error: array subscript is above array bounds
[-Werror=array-bounds]
port->info[k].id = 0;
^
cc1: some warnings being treated as errors
Makefile:777: recipe for target 'xvdisp.lo' failed
This does *NOT* happen with gcc-4.9.
The xorg guys think this has to be a gcc bug.
Here is the bug report on their bug tracker:
Bug #91031 https://bugs.freedesktop.org/show_bug.cgi?id=91031
See their bug report for a more detailed explaination why they blame gcc and
not their code.
I'm running/building with
- Distro: Arch Linux (rolling-release, up-to-date)
- gcc-5.1 is from the official Arch Linux repo.
- Intel x64_64 (Haswell) with -march=native and -mtune=native
I have the following build options set via /etc/makepkg.conf (which is used for
package compilation from source on Arch Linux):
CARCH="x86_64"
CHOST="x86_64-unknown-linux-gnu"
CPPFLAGS="-D_FORTIFY_SOURCE=2"
CFLAGS="-march=native -mtune=native -O3 -pipe -fstack-protector-strong
--param=ssp-buffer-size=4"
CXXFLAGS="-march=native -mtune=native -O3 -pipe -fstack-protector-strong
--param=ssp-buffer-size=4"
LDFLAGS="-Wl,-O2,--sort-common,--as-needed,-z,relro"
MAKEFLAGS="-j16"
DEBUG_CFLAGS="-g -fvar-tracking-assignments"
DEBUG_CXXFLAGS="-g -fvar-tracking-assignments"
Changing -O3 to -O2 makes the build complete without fatal errors and results
in a working xorg-server.
