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Verifies that a specified pointer is in the local heap (debug version only).

int _CrtIsValidHeapPointer( 
   const void *userData 



Pointer to the beginning of an allocated memory block.

_CrtIsValidHeapPointer returns TRUE if the specified pointer is in the local heap. Otherwise, the function returns FALSE.

The _CrtIsValidHeapPointer function is used to ensure that a specific memory address is within the local heap. The local heap refers to the heap created and managed by a particular instance of the C run-time library. If a dynamic-link library (DLL) contains a static link to the run-time library, it has its own instance of the run-time heap, and therefore its own heap, independent of the application's local heap. When _DEBUG is not defined, calls to _CrtIsValidHeapPointer are removed during preprocessing.

Because this function returns TRUE or FALSE, it can be passed to one of the _ASSERT macros to create a simple debugging error handling mechanism. The following example causes an assertion failure if the specified address is not located within the local heap:

_ASSERTE( _CrtIsValidHeapPointer( userData ) );

For more information about how _CrtIsValidHeapPointer can be used with other debug functions and macros, see Using Macros for Verification and Reporting. For information about how memory blocks are allocated, initialized, and managed in the debug version of the base heap, see Memory Management and the Debug Heap.

Routine Required header Compatibility



Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

For more compatibility information, see Compatibility in the Introduction.

Debug versions of C run-time libraries only.

// crt_isvalid.c
 * This program allocates a block of memory using _malloc_dbg
 * and then tests the validity of this memory by calling 
 * _CrtIsMemoryBlock,_CrtIsValidPointer, and _CrtIsValidHeapPointer.

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <crtdbg.h>

#define  TRUE   1
#define  FALSE  0

int main( void )
        char *my_pointer;

         * Call _malloc_dbg to include the filename and line number
         * of our allocation request in the header information
        my_pointer = (char *)_malloc_dbg( sizeof(char) * 10, 
        _NORMAL_BLOCK, __FILE__, __LINE__ );

        // Ensure that the memory got allocated correctly
        _CrtIsMemoryBlock((const void *)my_pointer, sizeof(char) * 10, 
        NULL, NULL, NULL );

         // Test for read/write accessibility
        if (_CrtIsValidPointer((const void *)my_pointer, 
        sizeof(char) * 10, TRUE))
                printf("my_pointer has read and write accessibility.\n");
                printf("my_pointer only has read access.\n");

        // Make sure my_pointer is within the local heap
        if (_CrtIsValidHeapPointer((const void *)my_pointer))
                printf("my_pointer is within the local heap.\n");
                printf("my_pointer is not located within the local"
                       " heap.\n");


my_pointer has read and write accessibility.
my_pointer is within the local heap.

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.