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Header File



Memory Routines


int _heapset(unsigned int fillvalue);


Fills the free blocks on the heap with a constant value.

_heapset checks the heap for consistency using the same methods as _heapchk. It then fills each free block in the heap with the value contained in the least significant byte of fillvalue. This function can be used to find heap-related problems. It does not guarantee that subsequently allocated blocks will be filled with the specified value.

Return Value

One of the following values:


The heap appears to be uncorrupted


No heap exists


A corrupted heap block has been found


 #include <windowsx.h>
 #include <malloc.h>
 #include <stdio.h>
 #include <stdlib.h>
 BOOL InitApplication(HINSTANCE hInstance);
 HWND InitInstance(HINSTANCE hInstance, int nCmdShow);
 LRESULT FAR PASCAL _export MainWndProc(HWND hWnd, UINT message,
             WPARAM wParam, LPARAM lParam);
 void ExampleHeapSet(HWND hWnd);
 #pragma argsused
 int PASCAL WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
         LPSTR lpCmdLine, int nCmdShow)
 MSG msg;      // message
   if (!InitApplication(hInstance))  // Initialize shared things
    return (FALSE); // Exits if unable to initialize
   /* Perform initializations that apply to a specific instance */
   if (!(InitInstance(hInstance, nCmdShow)))
    return (FALSE);
   /* Acquire and dispatch messages until a WM_QUIT message is received. */
   while (GetMessage(&msg, // message structure
    NULL, // handle of window receiving the message
    NULL, // lowest message to examine
    NULL))  // highest message to examine
   TranslateMessage(&msg); // Translates virtual key codes
   DispatchMessage(&msg);  // Dispatches message to window
   return (msg.wParam);  // Returns the value from PostQuitMessage
 BOOL InitApplication(HINSTANCE hInstance)
   WNDCLASS  wc;
   // Fill in window class structure with parameters that describe the
   // main window.
   wc.style = CS_HREDRAW | CS_VREDRAW; // Class style(s).
   wc.lpfnWndProc = (long (FAR PASCAL*)(void *,unsigned int,unsigned int, long ))MainWndProc; // Function to retrieve messages for
                 // windows of this class.
   wc.cbClsExtra = 0;  // No per-class extra data.
   wc.cbWndExtra = 0;  // No per-window extra data.
   wc.hInstance = hInstance; // Application that owns the class.
   wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
   wc.hCursor = LoadCursor(NULL, IDC_ARROW);
   wc.hbrBackground = GetStockObject(WHITE_BRUSH);
   wc.lpszMenuName = NULL;  // Name of menu resource in .RC file.
   wc.lpszClassName = "Example"; // Name used in call to CreateWindow.
   /* Register the window class and return success/failure code. */
   return (RegisterClass(&wc));
 HWND InitInstance(HINSTANCE hInstance, int nCmdShow)
   HWND  hWnd; // Main window handle.
   /* Create a main window for this application instance.  */
   hWnd = CreateWindow(
    "Example",                 // See RegisterClass() call.
    "Example _heapset 32 bit only",  // Text for window title bar.
    WS_OVERLAPPEDWINDOW,        // Window style.
    CW_USEDEFAULT,         // Default horizontal position.
    CW_USEDEFAULT,          // Default vertical position.
    CW_USEDEFAULT,            // Default width.
    CW_USEDEFAULT,        // Default height.
    NULL,                  // Overlapped windows have no parent.
    NULL,                  // Use the window class menu.
    hInstance,              // This instance owns this window.
    NULL                   // Pointer not needed.
   /* If window could not be created, return "failure" */
   if (!hWnd)
    return (FALSE);
   /* Make the window visible; update its client area; and return "success" */
   ShowWindow(hWnd, nCmdShow); // Show the window
   UpdateWindow(hWnd);     // Sends WM_PAINT message
   return (hWnd);        // Returns the value from PostQuitMessage
 void ExampleHeapSet(HWND hWnd)
   int hsts;
   char *buffer;
   if ( (buffer = (char *)malloc( 1 )) == NULL )
   hsts = _heapset( 'Z' );
   switch (hsts)
     case _HEAPOK:
       MessageBox(hWnd,"Heap is OK","Heap",MB_OK|MB_ICONINFORMATION);
     case _HEAPEMPTY:
       MessageBox(hWnd,"Heap is empty","Heap",MB_OK|MB_ICONINFORMATION);
     case _HEAPBADNODE:
       MessageBox(hWnd,"Bad node in heap","Heap",MB_OK|MB_ICONINFORMATION);
   free (buffer);
 #pragma argsused
 LRESULT FAR PASCAL _export MainWndProc(HWND hWnd, UINT message,
             WPARAM wParam, LPARAM lParam)
   switch (message) {
     case WM_CREATE:
       //Example _heapset
       return NULL;
     case WM_QUIT:
     case WM_DESTROY:  // message: window being destroyed
     default:      // Passes it on if unprocessed
       return (DefWindowProc(hWnd, message, wParam, lParam));