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malloc_verify

Syntax

 
#include <stdlib.h>

int malloc_verify(void);

Description

This function attempts to determine if the heap has been corrupted. It scans all the blocks allocated by malloc and handed to the application, and also all the free blocks maintained by malloc and free in the internal free list. Each block is checked for consistency of the hidden bookkeeping information recorded in it by malloc and free. The blocks on the free list are additionally validated by chasing all the next pointers in the linked list and checking them against limits for valid pointers (between 0x1000 and the data segment limit), and the alignment. (Unaligned pointers are probably corrupted, since malloc always returns a properly aligned storage.)

What happens when a bad block is found depends on the current malloc diagnostics level: for example, the block can be reported, or the program may be aborted. See section malloc_debug, for the details.

Return Value

If the program isn't aborted during the function's run (this depends on the current diagnostics level), malloc_verify returns 1 if the heap passes all tests, or zero of some of the tests failed.

Portability

ANSI/ISO C No
POSIX No (see note 1)

Notes:

  1. This function is available on many Unix systems.

Example

 
 if (malloc_verify() == 0)
   printf ("Heap corruption detected!\n");


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  Copyright 2004   by DJ Delorie     Updated Apr 2004