Re: Undefined use of weak symbols in gnulib

[Bruno Haible]

Hi Florian,

> This will become an urgent issue with glibc 2.34

Thank you for the early heads-up.

I would like to understand the scope and the severity of the issue.

You write:
> Dynamic linking with weak symbols is not very well-defined.  ...
> the code will crash if pthread_mutexattr_gettype is ever defined.

In which situations will it crash?

  (a) when the code is in an executable, that gets linked with '-lpthread'
      and that does not use dlopen()?
  (b) when the code is in an executable, that gets linked WITHOUT
      '-lpthread' and that does not use dlopen()?
  (c) when the code is in an executable, that gets linked WITHOUT
      '-lpthread' and that does a dlopen("libpthread.so.X")?

Under which conditions will it crash?

  ($) when the executable was built before glibc 2.34 and is run
      with glibc 2.34 ?
  (%) when the executable is built against glibc 2.34 and is run
      with glibc 2.34 ?

And if it crashes, will setting the environment variable LD_DYNAMIC_WEAK [1]
avoid the crash?

Bruno

[1] https://sourceware.org/legacy-ml/libc-hacker/2000-06/msg00029.html