Example (_udestroy -- Destroy a Heap) (Windows)

This example creates and opens a heap, performs operations on it, and then closes it. The program then calls _udestroy with the _FORCE parameter to force the destruction of the heap. _udestroy calls release_fn to return the memory to the system.

#include <windows.h>
#include <stdlib.h>
#include <stdio.h>
#include <umalloc.h>
static void* get_fn(Heap_t usrheap, size_t *length, int *clean)
{
    void *p;
    /* Round up to the next chunk size */
    *length = ((*length) / 65536) * 65536 + 65536;
    *clean = _BLOCK_CLEAN;
    p = VirtualAlloc(NULL, *length, MEM_COMMIT|MEM_RESERVE, PAGE_READWRITE);
    return (p);
}
static void release_fn(Heap_t usrheap, void *p, size_t size)
{
    VirtualFree(p, 0, MEM_RELEASE );
    return;
}
int main(void)
{
   void    *initial_block;
   Heap_t  myheap;
   char    *ptr;
   /* Call VirtualAlloc to get the initial block of memory */
   if (NULL == (initial_block =
       VirtualAlloc(NULL, 65536, MEM_COMMIT|MEM_RESERVE, PAGE_READWRITE)))
   {
      printf("VirtualAlloc error: %d.\n", GetLastError());
      exit(EXIT_FAILURE);
   }
   /* Create an expandable heap starting with the block declared earlier */
   if (NULL == (myheap = _ucreate(initial_block, 65536, _BLOCK_CLEAN,
                                  _HEAP_REGULAR, get_fn, release_fn))) {
      puts("_ucreate failed.");
      exit(EXIT_FAILURE);
   }
   if (0 != _uopen(myheap)) {
      puts("_uopen failed.");
      exit(EXIT_FAILURE);
   }
   /* Force user heap to grow */
   ptr = (char *)_umalloc(myheap, 100000);
   free(ptr);
   _uclose(myheap);
   if (0 != _udestroy(myheap, _FORCE)) {
      puts("_udestroy failed.");
      exit(EXIT_FAILURE);
   }
   if (FALSE == VirtualFree(initial_block, 0, MEM_RELEASE)) {
      printf("VirtualFree error: %d.\n", GetLastError());
      exit(EXIT_FAILURE);
   }
   return 0;
}