People have marked this post as a duplicate of this but it's actually not because I'm not asking what is a composite type but what is its purpose and i gave a use case where it could cause a harm for software developers and then asked if this should be undefined behavior instead.
I was reading that part of the C11 standard about composite types and i was just like : Why the heck on earth would someone do something like that ?
I mean i can't see anything interesting about that. I think this is very confusing for programmers. For the sake of example, let's say we had a function void f() that people used everywhere in the software, they just declare extern void f() and use it. The definition of the function is somewhere programmers don't care about; then one day, one smart guy needed to add an argument to that function and changed the definition to something like void f(int *ptr) {/* ..*/ return *ptr;}. The software will still compile happily but god, all that legacy code that used the old interface is screwed up with segfaults.
The code below is a demo :
/* main.c */
#include <stdio.h>
int f ();
int p = 5;
int main ()
{
int r = f (); /* This call will cause segfault */
int s = f (&p);
printf ("r=%d / s=%d \n", r, s);
return 0;
}
/* another_unit.c */
int f (int *ptr)
{
return *ptr;
}
I don't see the purpose of such a thing. In my opinion that should be undefined behavior or at least why do compilers like GCC don't say anything about it ?
