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Changes the size of a memory block that was allocated with _aligned_malloc or _aligned_offset_malloc (debug version only).

void * _aligned_realloc_dbg(
   void *memblock, 
   size_t size, 
   size_t alignment,
   const char *filename,
   int linenumber 

[in] memblock

The current memory block pointer.

[in] size

The size of the requested memory allocation.

[in] alignment

The alignment value, which must be an integer power of 2.

[in] filename

Pointer to the name of the source file that requested the realloc operation or NULL.

[in] linenumber

Line number in the source file where the realloc operation was requested or NULL.

_aligned_realloc_dbg returns a void pointer to the reallocated (and possibly moved) memory block. The return value is NULL if the size is zero and the buffer argument is not NULL, or if there is not enough available memory to expand the block to the given size. In the first case, the original block is freed. In the second, the original block is unchanged. The return value points to a storage space that is guaranteed to be suitably aligned for storage of any type of object. To get a pointer to a type other than void, use a type cast on the return value.

It is an error to reallocate memory and change the alignment of a block.

_aligned_realloc_dbg is a debug version of the _aligned_realloc function. When _DEBUG is not defined, each call to _aligned_realloc_dbg is reduced to a call to _aligned_realloc. Both _aligned_realloc and _aligned_realloc_dbg reallocate a memory block in the base heap, but _aligned_realloc_dbg accommodates several debugging features: buffers on either side of the user portion of the block to test for leaks, a block type parameter to track specific allocation types, and filename/linenumber information to determine the origin of allocation requests.

_aligned_realloc_dbg reallocates the specified memory block with slightly more space than the requested newSize. newSize might be greater or less than the size of the originally allocated memory block. The additional space is used by the debug heap manager to link the debug memory blocks and to provide the application with debug header information and overwrite buffers. The reallocation might result in moving the original memory block to a different location in the heap, as well as changing the size of the memory block. If the memory block is moved, the contents of the original block are overwritten.

In Visual C++ 2005, _aligned_realloc_dbg sets errno to ENOMEM if a memory allocation fails or if the amount of memory needed (including the overhead mentioned previously) exceeds _HEAP_MAXREQ. For information about this and other error codes, see errno, _doserrno, _sys_errlist, and _sys_nerr.

Also, _aligned_realloc_dbg validates its parameters. If alignment is not a power of 2, this function invokes the invalid parameter handler, as described in Parameter Validation. If execution is allowed to continue, this function returns NULL and sets errno to EINVAL.

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. For information about the allocation block types and how they are used, see Types of Blocks on the Debug Heap. For information about the differences between calling a standard heap function and its debug version in a debug build of an application, see Using the Debug Version Versus the Base Version.


Required header



For more compatibility information, see Compatibility in the Introduction.


Debug versions of C run-time libraries only.

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