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Problems with glibc - how to debug?


Hi All,

We have been having issues with versions of GLIBC that Red Hat has been 
distributing. Originally our problems appeared to be related to thread, 
so I replaced our threading needs (quite simple needs actually) with 
direct calls to clone(). This solved the problem on Red Hat 8 and related 
distros, but with Red Hat 9, Fedora and the latest Enterprise Linux 
editions, we are now seeing the same problem again.

Basically something is screwy with __libc_enable_async_cancel(), such 
that after a few open() calls we get a crash inside libc in this function 
(at least it appears that way). Strangely enough a slightly different 
build of our code works just fine, and doesn't appear to be doing 
anything different, although that build *did* have almost identical 
problems on Red Hat 8 when we were using pthreads. The same code has no 
issues with other distros, so I am at a loss as to what could be causing 
this. One thing we also found is that this is related to specific CPU 
versions of GLIBC - the 686 and Athlon optimised versions have this 
problem, but the 386 versions do not. Also static linking my programs 
also solves the problem (ie: only appears to happen in the dynamic libs, 
but it is possible the static libs are not 686 or Athlon optimised).

Also the other strange thing is that this appears to be related to 2.6 
kernel services back ported to the Red Hat 2.4 kernels. If we set the 
LD_ASSUME_KENERL=2.4.19, the problem goes away!

Any ideas?

Last time we ran into this problem I tried installing a debug version of 
glibc so that I could debug into the open() call and see exactly where 
the code is crashing, but for the life of me I could not get GDB to see 
any of the glibc symbols! Can someone point me at some step by step 
instructions on how to install a debug version of the glibc that comes 
with Red Hat 9 with debug symbols so I can debug into the code?

Any help would be greatly appreciated!

Thanks!

---
Kendall Bennett
Chief Executive Officer
SciTech Software, Inc.
Phone: (530) 894 8400
http://www.scitechsoft.com

~ SciTech SNAP - The future of device driver technology! ~


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