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realloc

From cppreference.com
< c‎ | memory
Revision as of 11:53, 24 October 2013 by P12 (Talk | contribs)

Defined in header <stdlib.h>
void *realloc( void *ptr, size_t new_size );

Reallocates the given area of memory. It must be previously allocated by malloc(), calloc() or realloc() and not yet freed with free, otherwise, the results are undefined.

The reallocation is done by either:

a) expanding or contracting the existing area pointed to by ptr, if possible. The contents of the area remain unchanged up to the lesser of the new and old sizes. If the area is expanded, the contents of the new part of the array are undefined.
b) allocating a new memory block of size new_size bytes, copying memory area with size equal the lesser of the new and the old sizes, and freeing the old block.

If there is not enough memory, the old memory block is not freed and null-pointer is returned.

If new_size is zero, the behavior is implementation defined (null pointer may be returned, or some non-null pointer may be returned that may not be used to access storage).

Contents

Parameters

ptr - pointer to the memory area to be reallocated
new_size - new size of the array

Return value

Pointer to the beginning of newly allocated memory or NULL if an error has occurred. The pointer must be deallocated with free().

Example

See also

C++ documentation for realloc