_umalloc - Reserve Memory Blocks from User Heap

Syntax

#include <umalloc.h>
void *_umalloc(Heap_t heap, size_t size);

umalloc allocates a memory block of size bytes from the heap you specify. Unlike _ucalloc, _umalloc does not initialize all bits to 0.
_umalloc works just like malloc, except that you specify the heap to use; malloc always allocates from the default heap. A debug version of this function, _debug_umalloc, is also provided.
If the heap does not have enough memory for the request, _umalloc calls the getmore_fn that you specified when you created the heap with _ucreate.
To reallocate or free memory allocated with _umalloc, use the non-heap-specific realloc and free. These functions always check what heap the memory was allocated from.

umalloc returns a pointer to the reserved space. If size was specified as 0, or if your getmore_fn cannot provide enough memory, _umalloc returns NULL. Passing _umalloc a heap that is not valid results in undefined behavior.

This example creates a heap and uses _umalloc to allocate memory from the heap.

#include <stdlib.h>
#include <stdio.h>
#include <umalloc.h>

int main(void)
{
   Heap_t  myheap;
   char    *ptr;

   /* Use default heap as user heap */
   myheap = _udefault(NULL);

   if (NULL == (ptr = _umalloc(myheap, 100))) {
      puts("Cannot allocate memory from user heap.");
      exit(EXIT_FAILURE);
   }
   free(ptr);
   return 0;
}

calloc
free
malloc
realloc
ucalloc
ucreate
Managing Memory" in the VisualAge C++ Programming Guide

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