Question

I have a buffer and want to do a test to see if the buffer has sufficient capacity I.e. find number of elements I can add to the buffer.

char *buffer = (char *)malloc(sizeof(char) * 10);

Doing a

int numElements = sizeof(buffer); 

does not return 10, any ideas on how I can accomplish this?

Answer 1

buffer is just a pointer without size information. However the malloc() routine will hold the size of the allocation you made so when you free() it, it frees the right amount of space. So unless you want to dive in the malloc() functionality, I recommend you just save the size of the allocation yourself. (for a possible implementation, see the example in the other API answer).