🚀 go-pugleaf

In article <1992Dec16.172748.24120@bernina.ethz.ch>, hoesel@igc.ethz.ch (Frans van Hoesel) writes:

> I have a problem in doing what I want to do in c.

> typedef void (*generic)();

>         f = (generic) printf;
>         g = (generic) abs;

> 	/* and now do something like :printf("some text %d\n",abs(i)
> 	  ), but using f and g instead !*/

> This isn't the right group to ask (I know), but propably the best

Asking elsewhere than in the right group is never best.  I'm taking
steps to move it to comp.lang.c, since it really is not a standard
question, but a generic C question.

As for how you'd do it,

(*(int (*)(const char *, ...))f)("some text %d\n",(*(int (*)(int))g)(i));

Note the casts on the functions!  The compiler may be using different
calling sequences depending on the argument pattern and return type, so
for the calls to work you must cast the pointers correctly.  (The two
"(*(" sequences may be replaced by "((" instead; I just happen to like
to follow my function pointers before calling them.)

> There is also a remark from my compiler on some constructs stating
> that void pointer cannot be cast to function pointers.  Is this
> allowed?

Only in the special case of a null pointer constant.  Object pointers
and function pointers are not, in general, interconvertible.

					der Mouse

			    mouse@larry.mcrcim.mcgill.edu