_rtl_heapwalk

Remonter à Alloc.h - Index

Header File

malloc.h

Prototype

int _rtl_heapwalk(_HEAPINFO *hi);

Description

Inspects the heap node by node.

Note: This function replaces _heapwalk which is obsolete.

_rtl_heapwalk assumes the heap is correct. Use _heapchk to verify the heap before using _rtl_heapwalk. _HEAPOK is returned with the last block on the heap. _HEAPEND will be returned on the next call to _rtl_heapwalk.

_rtl_heapwalk receives a pointer to a structure of type _HEAPINFO (declared in malloc.h). Note that the _HEAPINFO structure must be allocated on the heap (using malloc()). You cannot pass the address of a variable declared on the stack.

For the first call to _rtl_heapwalk, set the hi._pentry field to NULL. _rtl_heapwalk returns with hi._pentry containing the address of the first block.

hi._size	holds the size of the block in bytes.
hi._useflag	is a flag that is set to _USEDENTRY if the block is currently in use. If the block is free, hi._useflag is set to _FREEENTRY.

Return Value

This function returns one of the following values:

_HEAPBADNODE	A corrupted heap block has been found
_HEAPBADPTR	The _pentry field does not point to a valid heap block
_HEAPEMPTY	No heap exists
_HEAPEND	The end of the heap has been reached
_HEAPOK	The _heapinfo block contains valid information about the next heap block

Portability

	POSIX	ANSI C	ANSI C++	Win32	Win64	macOS
_rtl_heapwalk				+

Example

#include <stdio.h>
#include <malloc.h>
#include <alloc.h>
#define NUM_PTRS  10
#define NUM_BYTES 16

int main(void) {
    _HEAPINFO *hi;
    char *array[NUM_PTRS];
    int i;
    hi = (_HEAPINFO*) malloc(sizeof(_HEAPINFO));
    for (i = 0; i < NUM_PTRS; i++)
        array[i] = (char *) malloc(NUM_BYTES);
    for (i = 0; i < NUM_PTRS; i += 2)
        free(array[i]);
    hi->_pentry = NULL;
    printf("   Size   Status\n");
    printf("   ----   ------\n");
    while (_rtl_heapwalk(hi) == _HEAPOK)
        printf("%7u    %s\n", hi->_size, hi->_useflag ? "used" : "free");
    free(hi);
    return 0;
}