Syntax

#include <umalloc.h>
int _heapset(Heap_t heap, unsigned int fill);

• uheapset checks the heap you specify for minimal consistency by checking all allocated and freed objects on the heap (similar to _uheapchk). It then sets each byte of the heap's free objects to the value of fill.

  Using _uheapset can help you locate problems where your program continues to use a freed pointer to an object. After you set the free heap to a specific value, when your program tries to interpret the set values in the freed object as data, unexpected results occur, indicating a problem.

  _uheapset works just like _heapset, except that you specify the heap to check; _heapset always checks the default heap.

  Note: Using the _uheapchk, _uheapset, and _uheap_walk functions (and their equivalents for the default heap) may add overhead to each object allocated from the heap.

• uheapset returns one of the following values, defined in both <umalloc.h> and <malloc.h>:

• HEAPBADBEGIN
  The heap specified is not valid. It may have been closed or destroyed.
  _HEAPBADNODE
  A memory node is corrupted, or the heap is damaged.
  _HEAPEMPTY
  The heap has not been initialized.
  _HEAPOK
  The heap appears to be consistent.

This example creates a heap and allocates and frees memory from it. It then calls _uheapset to set the freed memory to a value.

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

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

   /* 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);
   }
   memset(ptr, 'A', 10);
   free(ptr);

   if (_HEAPOK != (rc = _uheapset(myheap, 'x'))) {
      switch(rc) {
         case _HEAPEMPTY:
            puts("The heap has not been initialized.");
            break;
         case _HEAPBADNODE:
            puts("A memory node is corrupted or the heap is damaged.");
            break;
         case _HEAPBADBEGIN:
            puts("The heap specified is not valid.");
            break;
      }
      exit(rc);
   }
   return 0;
}

• heapmin
  
• heapset
  
• uheapchk
  
• uheap_walk
  
• Managing Memory" in the VisualAge C++ Programming Guide
  
• Debugging Your Heaps" in the VisualAge C++ Programming Guide

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