`_aligned_malloc_dbg`

Article
02/07/2023

Allocates memory on a specified alignment boundary with extra space for a debugging header and overwrite buffers (debug version only).

Syntax

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

Parameters

size
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 allocation operation or NULL.

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

Return value

A pointer to the memory block that was allocated or NULL if the operation failed.

Remarks

_aligned_malloc_dbg is a debug version of the _aligned_malloc function. When _DEBUG isn't defined, each call to _aligned_malloc_dbg is reduced to a call to _aligned_malloc. Both _aligned_malloc and _aligned_malloc_dbg allocate a block of memory in the base heap, but _aligned_malloc_dbg offers 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_malloc_dbg allocates the memory block with slightly more space than the requested size. 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. When the block is allocated, the user portion of the block is filled with the value 0xCD, and each of the overwrite buffers are filled with 0xFD.

_aligned_malloc_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_malloc_dbg validates its parameters. If alignment isn't a power of 2 or size is zero, 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_malloc_dbg`	<crtdbg.h>

For more compatibility information, see Compatibility.

Libraries

Debug versions of C run-time libraries only.