heapchecknode

Header File

alloc.h

Category

Memory Routines

Prototype

int heapchecknode(void *node);

Description

Checks and verifies a single node on the heap.

If a node has been freed and heapchecknode is called with a pointer to the freed block, heapchecknode can return _BADNODE rather than the expected _FREEENTRY. This is because adjacent free blocks on the heap are merged, and the block in question no longer exists.

Return Value

One of the following values:

_BADNODE	Node could not be found
_FREEENTRY	Node is a free block
_HEAPCORRUPT	Heap has been corrupted
_HEAPEMPTY	No heap
_USEDENTRY	Node is a used block

Example

Copy Code

#include <stdio.h>
#include <alloc.h>
#define NUM_PTRS  10
#define NUM_BYTES 16
int main(void)
{
   char *array[ NUM_PTRS ];
   int i;
   for( i = 0; i < NUM_PTRS; i++ )
      array[ i ] = (char *) malloc( NUM_BYTES );
   for( i = 0; i < NUM_PTRS; i += 2 )
      free( array[ i ] );
   for( i = 0; i < NUM_PTRS; i++ )
   {
      printf( "Node %2d ", i );
      switch( heapchecknode( array[ i ] ) )
      {
         case _HEAPEMPTY:
              printf( "No heap.\n" );
              break;
         case _HEAPCORRUPT:
              printf( "Heap corrupt.\n" );
              break;
         case _BADNODE:
              printf( "Bad node.\n" );
              break;
         case _FREEENTRY:
              printf( "Free entry.\n" );
              break;
         case _USEDENTRY:
              printf( "Used entry.\n" );
              break;
         default:
              printf( "Unknown return code.\n" );
               break;
      }
   }
   return 0;
}

Portability

POSIX	Win32	ANSI C	ANSI C++
	+

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