`_aligned_realloc_dbg`

Article
02/07/2023

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

Syntax

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

Parameters

memblock
The current memory block pointer.

size
The size of the requested memory allocation.

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

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

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

Return value

_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 isn't NULL, or if there isn't 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 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's an error to reallocate memory and change the alignment of a block.

Remarks

_aligned_realloc_dbg is a debug version of the _aligned_realloc function. When _DEBUG isn't 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, and filename/linenumber information to determine the origin of allocation requests. Tracking specific allocation types with a block type parameter isn't a supported debug feature for aligned allocations. Aligned allocations will appear as a _NORMAL_BLOCK block type.

_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 extra 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 both move the original memory block to a different location in the heap, and change the size of the memory block. If the memory block is moved, the contents of the original block are overwritten.

_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 isn't 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 CRT debug heap details. For information about the allocation block types and how they're used, see Types of blocks on the debug heap. For information about the differences between standard heap functions and their debug versions, see Debug versions of heap allocation functions.

Requirements

Routine	Required header
`_aligned_realloc_dbg`	<crtdbg.h>

For more compatibility information, see Compatibility.

Libraries

Debug versions of C run-time libraries only.

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