Re: type-punning?

Hi

> This doesn't fix the problem. This merely reorganises the code in a form
> that the compiler may happen to not warn about.
>
> The problem is that dat is defined as char *. You can't pretend it's
> defined as a void *. The language doesn't let you.

are you saying that

---
int foo(void* bar)
{
  char *st = (char*)bar;
     :
}

 :
 :

char *bar;
 :

foo((void*)bar);
---

is not possible in C?

Are we using the same language?

> A fixed version looks
> like
>
> #include <stdlib.h>
> #include <stdio.h>
>
> static void *punme(void *dat, size_t newsize) {
>   return realloc(dat, newsize);
>
> }
>
> int main (void)
> {
>   char *dat = malloc(30);
>   char *newdat = punme(dat, 40); /* or call realloc directly */
>   if (newdat != NULL) dat = newdat;
>   printf("punme would have returned %d\n", (newdat == NULL ? 1 : 0));
>   return 0;
>
> }

Part of the "inessential detail" omitted is that
I use the return value of punme() for other purposes,
I specifically want to modify dat (char*) which I pass
to punme() by reference.

Is there really no way at all to modify a generic
pointer by passing a reference to it to a function?
Are C programmers condemned to return structs
(one member of which is the void* modified) whenever
we want to do generic programming??

Thanks!