Mailinglist Archive: opensuse-packaging (80 mails)

[Cristian Rodríguez <crrodriguez@xxxxxxxxxxxx>]

El 13/08/10 13:44, Cristian Morales Vega escribió:
> Hi,
>
> I'm getting
> "comp.c:42:3: warning: dereferencing type-punned pointer will break
> strict-aliasing rules"
>
> that translates to
>
> "I: Program is likely to break with new gcc. Try -fno-strict-aliasing.
> W: sipp strict-aliasing-punning comp.c:42, 46, 50"
>
> through post-build-checks.
>
> The thing is the offending code is
>
> "*(void **)(&comp_compress) = dlsym(handle, "comp_compress");"
>
> And the man page of dlsym explicitly says that is the correct way to do it:
>
>            /* 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(). */
>
>
> So, the question: could gcc -O2 really break that code? Or that's a
> false warning and I can be 100% safe ignoring it?

Even the example code in the manual triggers the warning, matz will
probably know where the bug really is ;)
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