How to check if a pointer is freed already in C?

Question

I would like to check if a pointer is freed already or not. How do I do this using gnu compiler set?

question from:https://stackoverflow.com/questions/8300853/how-to-check-if-a-pointer-is-freed-already-in-c

Answer 1

You can't. The way to track this would be to assign the pointer to 0 or NULL after freeing it. However as Fred Larson mentioned, this does nothing to other pointers pointing to the same location.

int* ptr = (int*)malloc(sizeof(int));
free(ptr);
ptr = NULL;