Re: [ANN] Lua 5.3.0 (rc3) now available

[Roberto Ierusalimschy <roberto@...>]

> On 2 January 2015 at 08:36, Luiz Henrique de Figueiredo
> <lhf@tecgraf.puc-rio.br> wrote:
> > We expect the compilation will go smoothly as usual
> > but please report any warnings or other glitches.
> 
> Compiling with gcc's --pedantic gives a single warning:
> 
> loadlib.c: In function ‘lsys_sym’:
> loadlib.c:151:21: warning: ISO C forbids conversion of object pointer
> to function pointer type [-Wpedantic]
>    lua_CFunction f = (lua_CFunction)dlsym(lib, sym);
>                      ^

This code has been like this for more than 10 years. Why did you wait for
'rc3' to complain?  :-)


> To get around this, you need to use this hack: (as seem in dlsym manpage/POSIX):
> 
>     double (*cosine)(double);
> 
>     /* 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");

This hack is as undefined in C99 as ours, but we can change that if
it removes the warning.

-- Roberto