strange segfault with pthreads in 0.9.28

jean-marie.verdun at jean-marie.verdun at
Mon May 15 14:45:38 UTC 2006

Hi Rupert,

Can you post a gdb output of the crash, like the call stack, this could 
perhaps help to better understand the matter.
I am close to the same situation than you, but on generic x86 (no specific 
c3) and everything is working fine for me. My base kernel is a 2.6.8 and I 
chroot into a 2.6.12 environment.


On Mon, 15 May 2006, Rupert Mazzucco wrote:

>> segfault.  A minimal reproduction is below.  Does anybody have an idea
>> what could be causing this?
>> Something has to be wrong on your site, I am using many apps that are
>> linked against libpthread and haven't seen this
> Yes, I'm afraid so.  Google found hardly any reference to such a problem.
> About the only one was, interestingly, an old linuxthreads faq on the
> site (can't find it now from the homepage), where the same
> symptom was described for apps compiled without -D_REENTRANT.
>> (only if you use uClibc-svn and the new linuxthreads)
> No, it's stock 0.9.28 release.  I would have tried a newer one, but are
> somewhat discouraged by what the list archives have to say about the status
> of the svn.  Binutils are 2.16.1, btw.  So just to verify that what I did
> _should_ normally work, or maybe someone can spot a problem there:
> - I used a recent buildroot snapshot to build a
> uClibc-09.28/gcc-3.4.6/binutils-2.16.1 toolchain and a minimal busybox root
> file system.  I had buildroot put the tools on the target fs to continue
> development there (so it's not really a cross-compiler, but a host
> compiler).
> - At first, I would chroot into the new root fs, because I had no bootable
> system yet.  Partly for testing the build environment, and partly because I
> thought it couldn't hurt, I then rebuilt gcc (I found I had to use the
> patched sources that know --host=i686-linux-uclibc) and uClibc, also
> upgraded make from 3.80 to 3.81 because of some dubious problem with vm
> exhaustion, replaced some busybox utils with GNU's because I (or rather,
> scripts) found them lacking functionality (find, tar, cpio, diff, patch),
> deleted ccache by hand because it annoyed me with its attempts to scribble
> around on my precious flash card, built some more stuff and eventually a
> kernel with all the above stuffed into an initramfs.  So all in all, I think
> I gave the toolchain a good workout, and didn't notice any problems.  But i
> seems now that was because nothing so far had touched pthreads.
> - I have to note that all that was done under the 2.4.26 kernel of the host
> system where I had my chroot jail.  I realized only later that using the
> built-with-2.6-headers-uclibc apps with this kernel was not guaranteed to
> work, but it seems like it did, and so far I didn't notice any difference in
> app behaviour in the chroot jail and with the real 2.6 kernel.
> It occurs to me while I write this, that for some reason this could have
> prevented the pthreads support from building properly.  Does that sound like
> a possibility?  Anyway, I'll have to to try and rebuild my toolchain under
> the new kernel now.
> Thank you,
> Rupert
>> Peter
>>> # cat > foo.c
>>> int main() {}
>>> # gcc foo.c
>>> # ./a.out
>>> # gcc foo.c -lpthread
>>> # ./a.out
>>> Segmentation fault
>>> # ldd a.out
>>> => /lib/ (0x40008000)
>>> => /lib/ (0x4001a000)
>>> => /lib/ (0x40000000)
>>> # gcc -D_REENTRANT foo.c -lpthread
>>> # ./a.out
>>> Segmentation fault
>>> # gcc -v
>>> Reading specs from /pkg/tools/lib/gcc/i686-linux-uclibc/3.4.6/specs
>>> Configured with: ../buildroot/toolchain_build_i686/gcc-3.4.6/configure
>> --host=i686-linux-uclibc --prefix=/pkg/tools --enable-shared
>> --enable-threads --disable-nls --with-arch=c3
> --with-sysroot=/pkg/uClibc-0.9.28
>> --enable-languages=c,c++,f77 --disable-__cxa_atexit
>>> (uClibc built with kernel headers from 2.6.16, buildroot snapshot
>> 20060418)
>> --
>> Peter S. Mazinger <ps dot m at gmx dot net>           ID: 0xA5F059F2
>> Key fingerprint = 92A4 31E1 56BC 3D5A 2D08  BB6E C389 975E A5F0 59F2
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