HeapValidate

The HeapValidate function attempts to validate a specified heap. The function scans all the memory blocks in the heap, and verifies that the heap control structures maintained by the heap manager are in a consistent state. You can also use the HeapValidate function to validate a single memory block within a specified heap, without checking the validity of the entire heap.

BOOL HeapValidate(
  HANDLE hHeap,  // handle to the heap of interest
  DWORD dwFlags, // bit flags that control heap access during 
                 // function operation
  LPCVOID lpMem  // optional pointer to individual memory block to 
                 // validate
);
 

Parameters

hHeap

Handle to the heap of interest. The HeapValidate function attempts to validate this heap, or a single memory block within this heap.

dwFlags

A set of bit flags that control heap access during function operation. The following bit flag has meaning:

Value	Meaning
HEAP_NO_SERIALIZE	Specifies that mutual exclusion is not used while the HeapValidate function accesses the heap.

lpMem

Pointer to a memory block within the specified heap. This parameter may be NULL.

If this parameter is NULL, the function attempts to validate the entire heap specified by hHeap.

If this parameter is not NULL, the function attempts to validate the memory block pointed to by lpMem. It does not attempt to validate the rest of the heap.

Return Values

If the specified heap or memory block is valid, the return value is nonzero.

If the specified heap or memory block is invalid, the return value is zero. On a system set up for debugging, the HeapValidate function then displays debugging messages that describe the part of the heap or memory block that is invalid, and stops at a hard-coded breakpoint so that you can examine the system to determine the source of the invalidity. The HeapValidate function does not set the thread's last error value. There is no extended error information for this function; do not call GetLastError.

Remarks

There are heap control structures for each memory block in a heap, and for the heap as a whole. When you use the HeapValidate function to validate a complete heap, it checks all of these control structures for consistency.

When you use HeapValidate to validate a single memory block within a heap, it checks only the control structures pertaining to that element. HeapValidate can only validate allocated memory blocks. Calling HeapValidate on a freed memory block will return FALSE because there are no control structures to validate.

If you want to validate the heap elements enumerated by the HeapWalk function, you should only call HeapValidate on the elements that have the PROCESS_HEAP_ENTRY_BUSY bit flag in the wFlags member of the PROCESS_HEAP_ENTRY structure. HeapValidate returns FALSE for all heap elements that do not have this bit set.

Serialization ensures mutual exclusion when two or more threads attempt to simultaneously allocate or free blocks from the same heap. There is a small performance cost to serialization, but it must be used whenever multiple threads allocate and free memory from the same heap. Setting the HEAP_NO_SERIALIZE flag eliminates mutual exclusion on the heap. Without serialization, two or more threads that use the same heap handle might attempt to allocate or free memory simultaneously, likely causing corruption in the heap. The HEAP_NO_SERIALIZE flag can, therefore, be safely used only in the following situations:

• The process has only one thread.
• The process has multiple threads, but only one thread calls the heap functions for a specific heap.
• The process has multiple threads, and the application provides its own mechanism for mutual exclusion to a specific heap.

QuickInfo

  Windows NT: Requires version 3.5 or later.
  Windows: Unsupported.
  Windows CE: Unsupported.
  Header: Declared in winbase.h.
  Import Library: Use kernel32.lib.

See Also

Memory Management Overview, Memory Management Functions, HeapCreate, HeapWalk, PROCESS_HEAP_ENTRY