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Verifies that a specified memory block is in the local heap and that it has a valid debug heap block type identifier (debug version only).

int _CrtIsMemoryBlock( 
   const void *userData,
   unsigned int size,
   long *requestNumber,
   char **filename,
   int *linenumber 


Pointer to the beginning of the memory block to verify.
Size of the specified block (bytes).
Pointer to the allocation number of the block or NULL.
Pointer to name of source file that requested the block or NULL.
Pointer to the line number in the source file or NULL.

Return Value

_CrtIsMemoryBlock returns TRUE if the specified memory block is located within the local heap and has a valid debug heap block type identifier; otherwise, the function returns FALSE.


The _CrtIsMemoryBlock function verifies that a specified memory block is located within the application's local heap and that it has a valid block type identifier. This function can also be used to obtain the object allocation order number and source file name/line number where the memory block allocation was originally requested. Passing non-NULL values for the requestNumber, filename, or linenumber parameters causes _CrtIsMemoryBlock to set these parameters to the values in the memory block's debug header, if it finds the block in the local heap. When _DEBUG is not defined, calls to _CrtIsMemoryBlock 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 will cause an assertion failure if the specified address is not located within the local heap:

_ASSERTE( _CrtIsMemoryBlock( userData, size, &requestNumber, &filename, &linenumber ) );

For more information about how _CrtIsMemoryBlock 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
_CrtIsMemoryBlock <crtdbg.h> Win 98, Win Me, Win NT, Win 2000, Win XP

For additional compatibility information, see Compatibility in the Introduction.


Debug versions of C run-time libraries only.


See the example for the _CrtIsValidHeapPointer topic.

See Also

Debug Functions | Run-Time Routines and .NET Framework Equivalents