_heapwalk
Traverses the heap and returns information about the next entry.
int _heapwalk( _HEAPINFO *entryinfo );
The _heapwalk function helps debug heap-related problems in programs. The function walks through the heap, traversing one entry per call, and returns a pointer to a structure of type _HEAPINFO that contains information about the next heap entry. The _HEAPINFO type, defined in Malloc.h, contains the following elements.
A call to _heapwalk that returns _HEAPOK stores the size of the entry in the _size field and sets the _useflag field to either _FREEENTRY or _USEDENTRY (both are constants defined in Malloc.h). To obtain this information about the first entry in the heap, pass _heapwalk a pointer to a _HEAPINFO structure whose _pentry member is NULL. If the operating system does not support _heapwalk(for example, Windows 98), the function returns _HEAPEND and sets errno to ENOSYS.
This function validates its parameter. If entryinfo is a null pointer, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, errno is set to EINVAL and the function returns _HEAPBADPTR.
Routine | Required header | Optional header |
|---|---|---|
_heapwalk | <malloc.h> | <errno.h> |
For more compatibility information, see Compatibility in the Introduction.
// crt_heapwalk.c
// This program "walks" the heap, starting
// at the beginning (_pentry = NULL). It prints out each
// heap entry's use, location, and size. It also prints
// out information about the overall state of the heap as
// soon as _heapwalk returns a value other than _HEAPOK
// or if the loop has iterated 100 times.
#include <stdio.h>
#include <malloc.h>
void heapdump(void);
int main(void)
{
char *buffer;
heapdump();
if((buffer = (char *)malloc(59)) != NULL)
{
heapdump();
free(buffer);
}
heapdump();
}
void heapdump(void)
{
_HEAPINFO hinfo;
int heapstatus;
int numLoops;
hinfo._pentry = NULL;
numLoops = 0;
while((heapstatus = _heapwalk(&hinfo)) == _HEAPOK &&
numLoops < 100)
{
printf("%6s block at %Fp of size %4.4X\n",
(hinfo._useflag == _USEDENTRY ? "USED" : "FREE"),
hinfo._pentry, hinfo._size);
numLoops++;
}
switch(heapstatus)
{
case _HEAPEMPTY:
printf("OK - empty heap\n");
break;
case _HEAPEND:
printf("OK - end of heap\n");
break;
case _HEAPBADPTR:
printf("ERROR - bad pointer to heap\n");
break;
case _HEAPBADBEGIN:
printf("ERROR - bad start of heap\n");
break;
case _HEAPBADNODE:
printf("ERROR - bad node in heap\n");
break;
}
}
Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
