On Fri, Mar 10, 2017 at 03:27:38PM +0000, Bernd Edlinger wrote:
> I have a question regarding the following code:
>
>
> char *p;
> [...]
> free(p);
> if (p != NULL) {
> printf("the pointer was non-zero\n");
> } else {
> printf("the pointer was null\n");
> }
>
>
> I would not have expected any problem with code like this,
> which uses the pointer value after the free function was called,
> as long as it does not dereference the pointer.
>
>
> But in the N1570 annex J.2, the following is written:
>
> "The behavior is undefined in the following circumstances:
> ...
> The value of a pointer that refers to space deallocated by a call to the
> free or realloc function is used (7.22.3)."
>
> So does this mean, that the above C code uses undefined behavior?
Annex J is informative only, and the things in there are quite shortened,
it's just a summary; I don't see anything in 7.22.3 itself that would make
this undefined behaviour.
Segher
