[Bug tree-optimization/49657] New: array subscript warnings when building gcc with -O2

[Bug tree-optimization/49657] New: array subscript warnings when building gcc with -O2

[dirtyepic at gentoo dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49657

           Summary: array subscript warnings when building gcc with -O2
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dirtyepic@gentoo.org


Building gcc-4.6.1 with BOOT_CFLAGS="-O2" causes a couple -Warray-bounds
warnings to be output.  I know there are several PRs open for bogus "above
array bounds" warnings but since these are triggered building GCC itself I
thought I'd report them.  There is also a "below array bounds" warning.

The warnings also appear in 4.6.0 but not 4.5.* IIRC.

~/gcc/gcc-4.6.1 $ ./configure --enable-languages=c
~/gcc/gcc-4.6.1 $ make BOOT_CFLAGS="-O2" bootstrap-lean


../../.././libgcc/../gcc/crtstuff.c: In function ‘frame_dummy’:
../../.././libgcc/../gcc/crtstuff.c:381:19: warning: array subscript is above
array bounds [-Warray-bounds]

../../.././libgcc/../gcc/crtstuff.c: In function ‘__do_global_ctors_aux’:
../../.././libgcc/../gcc/crtstuff.c:575:25: warning: array subscript is below
array bounds [-Warray-bounds]

../.././gcc/expmed.c: In function ‘init_expmed’:
../.././gcc/expmed.c:134:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:141:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:145:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:149:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:153:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:157:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:164:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:180:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:184:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:188:3: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:231:8: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:246:8: warning: array subscript is above array bounds
[-Warray-bounds]
../.././gcc/expmed.c:247:8: warning: array subscript is above array bounds
[-Warray-bounds]

[Bug tree-optimization/49657] array subscript warnings when building gcc with -O2

[dirtyepic at gentoo dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49657

--- Comment #1 from Ryan Hill <dirtyepic at gentoo dot org> 2011-07-06 04:54:56 UTC ---
Created attachment 24699
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24699
build log

[Bug tree-optimization/49657] array subscript warnings when building gcc with -O2

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49657

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-07-06 08:05:26 UTC ---
The expmed.c code is broken, not sure about the crtstuff one.

[Bug tree-optimization/49657] array subscript warnings when building gcc with -O2

[mirimiri66 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49657

--- Comment #3 from mirimiri66 at gmail dot com 2013-01-24 13:53:18 UTC ---
Created attachment 29265
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29265
gcc-4.6.3 QA Notices

[Bug tree-optimization/49657] array subscript warnings when building gcc with -O2

[mirimiri66 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49657

--- Comment #4 from mirimiri66 at gmail dot com 2013-01-24 13:54:20 UTC ---
Created attachment 29266
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29266
gentoo package systeme emerge --info

[Bug tree-optimization/49657] array subscript warnings when building gcc with -O2

[mirimiri66 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49657

mirimiri66 at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mirimiri66 at gmail dot com

--- Comment #5 from mirimiri66 at gmail dot com 2013-01-24 13:56:54 UTC ---
I get similar QA notices when compiling gcc-4.6.3 in gentoo. Gentoo package
notes instructed to report this here instead of filing a gentoo bug. I've got
these flags set in /etc/make.conf:

CFLAGS="-fomit-frame-pointer -march=native -O2 -pipe"

Is this something I need to address somehow?

Added QA Notices and gentoo package system emerge --info attachments.

[Bug tree-optimization/49657] array subscript warnings when building gcc with -O2

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49657

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |msebor at gcc dot gnu.org
         Resolution|---                         |WORKSFORME

--- Comment #6 from Martin Sebor <msebor at gcc dot gnu.org> ---
I suspect this is no longer a problem with current releases.  They all build
with -O2 and -Werror.