Does freeing an uninitialized pointer result in undefined behavior?

Question

If you have a pointer that is not initialized and, by mistake, try to free it, is this going to result in undefined behavior?

Like:

int main(void){

             


        

Answer 1

Yes, it is undefined behavior.

The pointer passed to free should be a pointer to a valid object allocated with malloc, calloc, realloc or a null pointer.

From C99:

(7.20.3.2p2) "If ptr is a null pointer, no action occurs. Otherwise, if the argument does not match a pointer earlier returned by the calloc, malloc, or realloc function, or if the space has been deallocated by a call to free or realloc, the behavior is undefined."