Determine size of dynamically allocated memory in C

Question

Is there a way in C to find out the size of dynamically allocated memory?

For example, after

char* p = malloc (100);

Is there

Answer 1

There is no standard way to find this information. However, some implementations provide functions like msize to do this. For example:

• _msize on Windows
• malloc_size on MacOS
• malloc_usable_size on systems with glibc

Keep in mind though, that malloc will allocate a minimum of the size requested, so you should check if msize variant for your implementation actually returns the size of the object or the memory actually allocated on the heap.