Incorrect IFUNC use in libpthread for fork, vfork wrapper [BZ #19861]

[Florian Weimer]

On 03/30/2016 09:51 PM, Richard Henderson wrote:

> Come to think of it, we had the same situation of the same symbol version being
> provided by two libraries prior to removing fork from libpthread too, so when
> providing compatibility symbols we must be mindful of that -- proper
> dependencies on libpthread may well not exist.

Considering that libpthread has a DT_NEEDED entry for libc.so.6, doe we 
actually need the compatibility wrapper?

I removed it, built a special libdofork.so which has a DT_NEEDED entry 
for libpthread.so.0 only, and got this with a glibc built that doesn't 
have the compatibility wrapper:

      12074:     symbol=fork;  lookup in file=/tmp/boom [0]
      12074:     symbol=fork;  lookup in file=./nptl/libpthread.so.0 [0]
      12074:     symbol=fork;  lookup in file=./libdofork.so [0]
      12074:     symbol=fork;  lookup in file=./libc.so.6 [0]
      12074:     binding file ./libdofork.so [0] to ./libc.so.6 [0]: 
normal symbol `fork' [GLIBC_2.2.5]

So it seems to work just as before.

The difference will be visible with dlopen, but will that matter?

Florian