malc writes:
> On Sun, 26 Nov 2006, Andrew Haley wrote:
>
> [..snip..]
> > union
> > {
> > void *barf;
> > void (*fptr) (void);
> > } bilge;
> >
> > bilge.barf = dlsym (NULL, "dummy");
> > funcs.dummy = bilge.fptr;
>
> The only thing, conformance wise, that can be different here is the
> fact that (according to the link bellow) type-prunning is allowed
> for unions. This does not change the fact that `void *' and any
> pointer to function are incompatible.
Are we talking ISO C or GNU C here? This is OK for GNU C, and I think
for POSIX.
> However i'm not targetting standard C
So why are you using -pedantic? -pedantic is only for strict ISO C.
> (i wouldn't know if it's possible to implement `dlsym' without
> falling into undefined/specified behavior on such a system at all).
>
> http://standards.ieee.org/reading/ieee/interp/1003.1-2001/1003.1-2001-04.html
> > > P.S. It seems like i can use the tripple casting trick once again
> > > instead of straightforward `struct.field', but this again begs
> > > the question of portability/conformance.
> >
> > Why are you using the "triple casting trick"? All it can possibly do
> > is silence a warning; it won't make the code correct.
>
> Less typing and:
> http://www.opensolaris.org/jive/thread.jspa?threadID=1923&tstart=0
Ths one, I guess:
...
* The cast below is the correct way to handle the problem.
* The (void *) cast is to avoid a GCC warning like:
* "warning: dereferencing type-punned pointer will break \
* strict-aliasing rules"
* which is wrong this code. (void *) introduces a compatible
* intermediate type in the cast list.
*/
count -= got, *(char **)(void *)&buffer += size * got;
I'm not convinced this hackery is correct by my reading of ISO C, and
in any case it's pointless. It could be replaced by:
count -= got, buffer = (char*)buffer + (size * got);
Andrew.
