[gentoo-user] valgrind showing glibc warnings

[gentoo-user] valgrind showing glibc warnings

[Crístian Viana]

[-- Attachment #1: Type: text/plain, Size: 863 bytes --]

hi,

when I use valgrind, it shows hundreds of warnings related to glibc. here's
one example, from "valgrind ls":

==10023== Use of uninitialised value of size 8
==10023==    at 0x55605A4: (within /lib64/libc-2.10.1.so)
==10023==    by 0x5560111: (within /lib64/libc-2.10.1.so)
==10023==    by 0x4A1E62C: _vgnU_freeres (in
/usr/lib64/valgrind/amd64-linux/vgpreload_core.so)
==10023==    by 0x548CE84: (within /lib64/libc-2.10.1.so)
==10023==    by 0x548CEF4: exit (in /lib64/libc-2.10.1.so)
==10023==    by 0x40864D: (within /bin/ls)
==10023==    by 0x5476A25: (below main) (in /lib64/libc-2.10.1.so)

while that happens, I can't use valgrind because there's too much noise
besides my program's [possible] memory errors.

any idea of why is this happening? I reemerged =sys-libs/glibc-2.10.1-r1 but
nothing has changed.

cheers,
Crístian.

[-- Attachment #2: Type: text/html, Size: 1289 bytes --]

Re: [gentoo-user] valgrind showing glibc warnings

[Jacob Todd]

[-- Attachment #1: Type: text/plain, Size: 1139 bytes --]

On Thu, Mar 25, 2010 at 11:09:36AM -0300, Crístian Viana wrote:
> hi,
> 
> when I use valgrind, it shows hundreds of warnings related to glibc. here's
> one example, from "valgrind ls":
> 
> ==10023== Use of uninitialised value of size 8
> ==10023==    at 0x55605A4: (within /lib64/libc-2.10.1.so)
> ==10023==    by 0x5560111: (within /lib64/libc-2.10.1.so)
> ==10023==    by 0x4A1E62C: _vgnU_freeres (in
> /usr/lib64/valgrind/amd64-linux/vgpreload_core.so)
> ==10023==    by 0x548CE84: (within /lib64/libc-2.10.1.so)
> ==10023==    by 0x548CEF4: exit (in /lib64/libc-2.10.1.so)
> ==10023==    by 0x40864D: (within /bin/ls)
> ==10023==    by 0x5476A25: (below main) (in /lib64/libc-2.10.1.so)
> 
> while that happens, I can't use valgrind because there's too much noise
> besides my program's [possible] memory errors.
> 
> any idea of why is this happening? I reemerged =sys-libs/glibc-2.10.1-r1 but
> nothing has changed.
> 
> cheers,
> Crístian.
You may want to look into supressions. There's an option called --gen-suppressions.
See the man page for details.

-- 
I am a man who does not exist for others.

[-- Attachment #2: Type: application/pgp-signature, Size: 198 bytes --]

[gentoo-user] Re: valgrind showing glibc warnings

[Nikos Chantziaras]

On 03/25/2010 04:09 PM, Crístian Viana wrote:
> hi,
>
> when I use valgrind, it shows hundreds of warnings related to glibc.

Rebuild valgrind.  This usually fixes this.

Re: [gentoo-user] Re: valgrind showing glibc warnings

[Crístian Viana]

[-- Attachment #1: Type: text/plain, Size: 346 bytes --]

I think --gen-suppressions may be a too "complicated" solution. valgrind
shouldn't find *any* warnings from the libraries of my system at all. either
valgrind is doing something wrong or there's really some errors on glibc. in
every other system I try, valgrind runs fine.

I rebuilt valgrind, but it didn't help.

I'm running amd64, by the way.

[-- Attachment #2: Type: text/html, Size: 429 bytes --]

Re: [gentoo-user] Re: valgrind showing glibc warnings

[Jacob Todd]

[-- Attachment #1: Type: text/plain, Size: 226 bytes --]

On Thu, Mar 25, 2010 at 03:31:19PM -0300, Crístian Viana wrote:
> either valgrind is doing something wrong or there's really some errors on
> glibc.

I wouldn't doubt it.

-- 
I am a man who does not exist for others.

[-- Attachment #2: Type: application/pgp-signature, Size: 198 bytes --]

[gentoo-user] Re: valgrind showing glibc warnings

[Nikos Chantziaras]

On 03/25/2010 05:36 PM, Jacob Todd wrote:
> On Thu, Mar 25, 2010 at 03:31:19PM -0300, Crístian Viana wrote:
>> either valgrind is doing something wrong or there's really some errors on
>> glibc.
>
> I wouldn't doubt it.

There are always errors everywhere :P  The problem is you shouldn't see 
them since you're only interested in those in your own application.

Anyway, in this case, the "error" lies in that glibc recently started 
using sse instructions to speed up some string operations on 
intel-compatible CPUs, and Valgrind barks at those unless it has access 
to the debugging symbols.  On other distros this is no issue since they 
make sure not to strip the libraries in question, or provide installable 
*-debug packages.  Gentoo doesn't provide this fine-grained debugging 
support, and you have to build using splitdebug in FEATURES.

[gentoo-user] Re: valgrind showing glibc warnings

[Nikos Chantziaras]

On 03/25/2010 08:31 PM, Crístian Viana wrote:
> I think --gen-suppressions may be a too "complicated" solution. valgrind
> shouldn't find *any* warnings from the libraries of my system at all.
> either valgrind is doing something wrong or there's really some errors
> on glibc. in every other system I try, valgrind runs fine.
>
> I rebuilt valgrind, but it didn't help.
>
> I'm running amd64, by the way.

On AMD64 you *must* build glibc with splitdebug in FEATURES.  And I 
think the very latest glibc versions also require splitdebug on x86 too. 
  And after that you must probably rebuild valgrind again :P

After you've built glibc with splitdebug, there should be no more 
warnings in valgrind.