Header File 

malloc.h 

Category 

Memory Routines 

Prototype 

size_t _msize(void *block); 

Description 

Returns the size of a heap block. 

_msize returns the size of the allocated heap block whose address is block. The block must have been allocated with malloc, calloc, or realloc. The returned size can be larger than the number of bytes originally requested when the block was allocated. 

Return Value 

_msize returns the size of the block in bytes. 

Example  

#include <malloc.h>        /* malloc() _msize() */
#include <stdio.h>            /* printf() */
int main( )
{
  int size;
  int *buffer;
  buffer = malloc(100 * sizeof(int));
  size = _msize(buffer);
  printf("Allocated %d bytes for 100 integers\n", size);
  return(0);
}

Portability