Re: [PATCH] Fix aliasing violation tst-rec-dlopen

[Pedro Alves <palves at redhat dot com>]

On 12/15/2015 09:49 AM, Florian Weimer wrote:
> Some GCC versions warn about this.  It's a clear misuse (presumably to
> avoid writing down the funny function pointer type), so I propose to fix
> this, instead of assuming that GCC will do the right thing.
> 

It's actually the form suggested in the dlopen/dlsym man page's EXAMPLE section:

~~~
           /* Writing: cosine = (double (*)(double)) dlsym(handle, "cos");
              would seem more natural, but the C99 standard leaves
              casting from "void *" to a function pointer undefined.
              The assignment used below is the POSIX.1-2003 (Technical
              Corrigendum 1) workaround; see the Rationale for the
              POSIX specification of dlsym(). */

           *(void **) (&cosine) = dlsym(handle, "cos");
~~~

http://linux.die.net/man/3/dlopen

Thanks,
Pedro Alves