As Joan said,
it is safe to use the referencing (or overpointing) of the pointers
for their stack passing (in any (de-)allocation contexts of the same process) :) :
extern void lib_alloc(int** ppInt);
extern void lib_free(int** ppInt);
void loc_test()
{
int* pInt(NULL);
lib_alloc(&pInt);
lib_free(&pInt);
}