| Platform SDK: Memory |
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 heap DWORD dwFlags, // heap access options LPCVOID lpMem // optional pointer to memory block );
| Value | Meaning |
|---|---|
| HEAP_NO_SERIALIZE | Specifies that mutual exclusion is not used while the HeapValidate function accesses the heap. |
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.
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.
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 PROCESS_HEAP_ENTRY_BUSY 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 value 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 value can, therefore, be safely used only in the following situations:
Validating a heap may degrade performance, especially on symmetric multiprocessing (SMP) computers. The side effects may last until the process ends.
Note To guard against an access violation, use structured exception handling to protect any code that writes to or reads from a heap. For more information on structured exception handling with memory accesses, see Reading and Writing and Structured Exception Handling.
Windows NT/2000: Requires Windows NT 3.5 or later.
Windows 95/98: Unsupported.
Header: Declared in Winbase.h; include Windows.h.
Library: Use Kernel32.lib.
Memory Management Overview, Memory Management Functions, HeapCreate, HeapWalk, PROCESS_HEAP_ENTRY