`_recalloc`

Article
02/07/2023

A combination of realloc and calloc. Reallocates an array in memory and initializes its elements to 0.

Syntax

void *_recalloc(
   void *memblock
   size_t num,
   size_t size
);

Parameters

memblock
Pointer to previously allocated memory block.

number
Number of elements.

size
Length in bytes of each element.

Return value

_recalloc returns a void pointer to the reallocated (and possibly moved) memory block.

If there isn't enough available memory to expand the block to the given size, the original block is left unchanged, and NULL is returned.

If the requested size is zero, then the block pointed to by memblock is freed; the return value is NULL, and memblock is left pointing at a freed block.

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.

Remarks

The _recalloc function changes the size of an allocated memory block. The memblock argument points to the beginning of the memory block. If memblock is NULL, _recalloc behaves the same way as calloc and allocates a new block of number * size bytes. Each element is initialized to 0. If memblock isn't NULL, it should be a pointer returned by a previous call to calloc, malloc, or realloc.

Because the new block can be in a new memory location, the pointer returned by _recalloc isn't guaranteed to be the pointer passed through the memblock argument.

_recalloc sets errno to ENOMEM if the memory allocation fails or if the amount of memory requested exceeds _HEAP_MAXREQ. For information on this and other error codes, see errno, _doserrno, _sys_errlist, and _sys_nerr.

recalloc calls realloc in order to use the C++ _set_new_mode function to set the new handler mode. The new handler mode indicates whether, on failure, realloc is to call the new handler routine as set by _set_new_handler. By default, realloc doesn't call the new handler routine on failure to allocate memory. You can override this default behavior so that, when _recalloc fails to allocate memory, realloc calls the new handler routine in the same way that the new operator does when it fails for the same reason. To override the default, call

_set_new_mode(1);

early in the program, or link with NEWMODE.OBJ.

When the application is linked with a debug version of the C run-time libraries, _recalloc resolves to _recalloc_dbg. For more information about how the heap is managed during the debugging process, see The CRT debug heap.

_recalloc is marked __declspec(noalias) and __declspec(restrict), meaning that the function is guaranteed not to modify global variables, and that the pointer returned isn't aliased. For more information, see noalias and restrict.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Routine	Required header
`_recalloc`	<stdlib.h> and <malloc.h>

For more compatibility information, see Compatibility.