Strange linking problem (MIPS, n32): wrong version node for libpthread!

["Kaz Kylheku" <kaz at zeugmasystems dot com>]

Hi Everyone,

I've discovered a silly problem on (MIPS, n32 ABI, gcc 4.1.1, glibc 2.5, 
binutils 2.17, ...).

I have a shared library which calls pthread functions. It is linked 
with -pthread. However, this -pthread is not enough to actually link it to 
libpthread.so. If you run ``ldd'' on the library image, libpthread is not 
mentioned anywhere!

This is very sneaky. We've been developing a very large and complex 
application for quite a long time, and the problem has gone unnoticed. The 
system runs, passes QA tests, etc.

What happens is that because the library doesn't depend on libpthread.so as 
it should, it doesn't request the appropriate symbol version node. Its 
references to pthread somehow get resolved to GLIBC_2.0.

So for instance pthread_create doesn't go to __pthread_create_2_1 but to 
__pthread_create_2_0. And this means that the stack size attribute set up in 
the pthread_attr_t parameter is ignored! So the virtual memory footprint of 
the application suite is far larger than what it should be due to all the 
threads mmap'ping the default 8 megs of stack.

If you add -lpthread when linking the library, it fixes the problem. (I've 
verified it in a small repro program, not the real app, but it's obvious it 
should work).

But this -lpthread should not be necessary if -pthread is already there, 
should it? It's a hack workaround.

This is probably in the wrong mailing list, sorry folks. Happy New Year, 
etc.