HeapSetInformation function (heapapi.h)

Enables features for a specified heap.

Syntax

BOOL HeapSetInformation(
  [in, optional] HANDLE                 HeapHandle,
  [in]           HEAP_INFORMATION_CLASS HeapInformationClass,
  [in]           PVOID                  HeapInformation,
  [in]           SIZE_T                 HeapInformationLength
);

Parameters

[in, optional] HeapHandle

A handle to the heap where information is to be set. This handle is returned by either the HeapCreate or GetProcessHeap function.

[in] HeapInformationClass

The class of information to be set. This parameter can be one of the following values from the HEAP_INFORMATION_CLASS enumeration type.

Value	Meaning
HeapCompatibilityInformation 0	Enables heap features. Only the low-fragmentation heap (LFH) is supported. However, it is not necessary for applications to enable the LFH because the system uses the LFH as needed to service memory allocation requests. Windows XP and Windows Server 2003:  The LFH is not enabled by default. To enable the LFH for the specified heap, set the variable pointed to by the HeapInformation parameter to 2. After the LFH is enabled for a heap, it cannot be disabled. The LFH cannot be enabled for heaps created with HEAP_NO_SERIALIZE or for heaps created with a fixed size. The LFH also cannot be enabled if you are using the heap debugging tools in Debugging Tools for Windows or Microsoft Application Verifier. When a process is run under any debugger, certain heap debug options are automatically enabled for all heaps in the process. These heap debug options prevent the use of the LFH. To enable the low-fragmentation heap when running under a debugger, set the _NO_DEBUG_HEAP environment variable to 1.
HeapEnableTerminationOnCorruption 1	Enables the terminate-on-corruption feature. If the heap manager detects an error in any heap used by the process, it calls the Windows Error Reporting service and terminates the process. After a process enables this feature, it cannot be disabled. Windows Server 2003 and Windows XP:  This value is not supported until Windows Vista and Windows XP with SP3. The function succeeds but the HeapEnableTerminationOnCorruption value is ignored.
HeapOptimizeResources 3	If HeapSetInformation is called with HeapHandle set to NULL, then all heaps in the process with a low-fragmentation heap (LFH) will have their caches optimized, and the memory will be decommitted if possible. If a heap pointer is supplied in HeapHandle, then only that heap will be optimized. Note that the HEAP_OPTIMIZE_RESOURCES_INFORMATION structure passed in HeapInformation must be properly initialized. Note  This value was added in Windows 8.1.

[in] HeapInformation

The heap information buffer. The format of this data depends on the value of the HeapInformationClass parameter.

If the HeapInformationClass parameter is HeapCompatibilityInformation, the HeapInformation parameter is a pointer to a ULONG variable.

If the HeapInformationClass parameter is HeapEnableTerminationOnCorruption, the HeapInformation parameter should be NULL and HeapInformationLength should be 0

[in] HeapInformationLength

The size of the HeapInformation buffer, in bytes.

Return value

If the function succeeds, the return value is nonzero.

If the function fails, the return value is 0 (zero). To get extended error information, call GetLastError.

Remarks

To retrieve the current settings for the heap, use the HeapQueryInformation function.

Setting the HeapEnableTerminateOnCorruption option is strongly recommended because it reduces an application's exposure to security exploits that take advantage of a corrupted heap.

Examples

The following example shows you how to enable the low-fragmentation heap.

#include <windows.h>
#include <tchar.h>
#include <stdio.h>

#define HEAP_LFH 2

int __cdecl _tmain()
{
    BOOL bResult;
    HANDLE hHeap;
    ULONG HeapInformation;

    //
    // Enable heap terminate-on-corruption. 
    // A correct application can continue to run even if this call fails, 
    // so it is safe to ignore the return value and call the function as follows:
    // (void)HeapSetInformation(NULL, HeapEnableTerminationOnCorruption, NULL, 0);
    // If the application requires heap terminate-on-corruption to be enabled, 
    // check the return value and exit on failure as shown in this example.
    //
    bResult = HeapSetInformation(NULL,
                                 HeapEnableTerminationOnCorruption,
                                 NULL,
                                 0);

    if (bResult != FALSE) {
        _tprintf(TEXT("Heap terminate-on-corruption has been enabled.\n"));
    }
    else {
        _tprintf(TEXT("Failed to enable heap terminate-on-corruption with LastError %d.\n"),
                 GetLastError());
        return 1;
    }

    //
    // Create a new heap with default parameters.
    //
    hHeap = HeapCreate(0, 0, 0);
    if (hHeap == NULL) {
        _tprintf(TEXT("Failed to create a new heap with LastError %d.\n"),
                 GetLastError());
        return 1;
    }

    //
    // Enable the low-fragmentation heap (LFH). Starting with Windows Vista, 
    // the LFH is enabled by default but this call does not cause an error.
    //
    HeapInformation = HEAP_LFH;
    bResult = HeapSetInformation(hHeap,
                                 HeapCompatibilityInformation,
                                 &HeapInformation,
                                 sizeof(HeapInformation));
    if (bResult != FALSE) {
        _tprintf(TEXT("The low-fragmentation heap has been enabled.\n"));
    }
    else {
        _tprintf(TEXT("Failed to enable the low-fragmentation heap with LastError %d.\n"),
                 GetLastError());
        return 1;
    }

    return 0;
}

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps | UWP apps]
Minimum supported server	Windows Server 2003 [desktop apps | UWP apps]
Target Platform	Windows
Header	heapapi.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll

See also

GetProcessHeap

Heap Functions

HeapCreate

HeapQueryInformation

Memory Management Functions