Undefined behavior or not?

[Bernd Edlinger]

Hi,

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?


Thanks
Bernd.