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

by

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;

More Related Contents:

  1. How does free know how much to free?
  2. Does free(ptr) where ptr is NULL corrupt memory?
  3. Is the compiler allowed to recycle freed pointer variables?
  4. Should one really set pointers to `NULL` after freeing them?
  5. C – Accessing data AFTER memory has been free()ed?
  6. How are we able to access the pointer after deallocating the memory?
  7. C pointer to array/array of pointers disambiguation
  8. What REALLY happens when you don’t free after malloc before program termination?
  9. Create a pointer to two-dimensional array
  10. Pointers in C: when to use the ampersand and the asterisk?
  11. Setting variable to NULL after free
  12. What is an opaque pointer in C?
  13. What is the reason for using a double pointer when adding a node in a linked list?
  14. Post-increment on a dereferenced pointer?
  15. What exactly is a C pointer if not a memory address?
  16. Reversing a string in C
  17. Why do I need to use type** to point to type*?
  18. What does malloc(0) return? [duplicate]
  19. Using intptr_t instead of void*?
  20. Does C99 guarantee that arrays are contiguous?
  21. Order of operations for dereference and bracket-ref in C
  22. Is typedef’ing a pointer type considered bad practice? [duplicate]
  23. behaviour of malloc(0)
  24. Arrow Operator vs. Dot Operator [closed]
  25. C: Correctly freeing memory of a multi-dimensional array
  26. “int *nums = {5, 2, 1, 4}” causes a segmentation fault
  27. Why exactly should I not call free() on variables not allocated by malloc()?
  28. Directly assigning values to C Pointers
  29. Returning a struct pointer
  30. Casting void pointers

Leave a Comment