Re: Functions with different versions in libc and libpthread

["H . J . Lu" <hjl at valinux dot com>]

On Thu, Nov 09, 2000 at 12:23:18AM -0800, Ulrich Drepper wrote:
> "H . J . Lu" <hjl@valinux.com> writes:
> 
> > Some functions have different versions in libc and libpthread. For
> > example, pread has GLIBC_2.1 in libc and GLIBC_2.2 in libpthread.
> > I can imagine potential problems with it. Shouldn't a fuction have
> > the same verion cross all libraries?
> 
> The names, although the same in all libraries, are completely
> separated.  They don't stand alone, they are used as a tuple
> (library,version).  It doesn't matter whether a symbol has different
> names in different DSOs.
> 

I am enclosing a testcase here taken from glibc 2.2:

# ldd /usr/lib/librt.so
        libc.so.6 => /lib/libc.so.6 (0x40023000)
        libpthread.so.0 => /lib/libpthread.so.0 (0x40149000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
# make
cc -D_GNU_SOURCE -I.   -c -o tst-aio64.o tst-aio64.c
cc -o test1 tst-aio64.o -lpthread -lrt
cc -o test2 tst-aio64.o -lrt
./test1
aio_write test ok
aio_read test ok
lio_listio (write) test ok
aio_fsync (aio_write) test ok
finished3
finished2
finished
./test2
make: *** wait: No child processes.  Stop.
make: *** Waiting for unfinished jobs....
make: *** wait: No child processes.  Stop.
# nm test1 | grep pread 
	U pread@@GLIBC_2.2
# nm test2 | grep pread
	U pread@@GLIBC_2.1
# ldd test2
        librt.so.1 => /lib/librt.so.1 (0x40023000)
        libc.so.6 => /lib/libc.so.6 (0x40035000)
        libpthread.so.0 => /lib/libpthread.so.0 (0x4015b000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

Even though libpthread.so.0 is linked with test2. But the wrong pread
is used.


-- 
H.J. Lu (hjl@valinux.com)