strange segfault with pthreads in 0.9.28

[Peter S. Mazinger]

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
> uclibc.org site (can't find it now from the homepage), where the same
> symptom was described for apps compiled without -D_REENTRANT.

I interpret -D_REENTRANT as of glibc = __UCLIBC_HAS_THREADS__ in uClibc (mostly)

maybe some header checks REENTRANT, though I am not aware of it

> > (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,

was this 'memory exhausted' maybe? Do you have disabled 
MALLOC_GLIBC_COMPAT per chance? I can't recall anyone having problems w/ 
make-3.80

> 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.

well, if you want to switch between 2.4 and 2.6, I would suggest you use 
2.4 kernels to build everything

Peter

> 
> 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
> > >         libpthread.so.0 => /lib/libpthread.so.0 (0x40008000)
> > >         libc.so.0 => /lib/libc.so.0 (0x4001a000)
> > >         ld-uClibc.so.0 => /lib/ld-uClibc.so.0 (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
> > 
> 
> 

-- 
Peter S. Mazinger <ps dot m at gmx dot net>           ID: 0xA5F059F2
Key fingerprint = 92A4 31E1 56BC 3D5A 2D08  BB6E C389 975E A5F0 59F2