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

comp.lang.c FAQ list · Question 7.27 -

Q. So can I query the malloc package to find out how big an allocated block is?

A. Unfortunately, there is no standard or portable way. (Some compilers provide nonstandard extensions.) If you need to know, you'll have to keep track of it yourself. (See also question 7.28.)