< cpp‎ | memory‎ | c
Revision as of 20:13, 31 May 2013 by P12bot (Talk | contribs)

Defined in header <cstdlib>
void* realloc( void* ptr, std::size_t new_size );

Reallocates the given area of memory. It must be previously allocated by Template:rlpf, Template:rlpf or realloc() and not yet freed with Template:rlpf, 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.



Because reallocation may involve bytewise copying (regardless of whether it's to expand or to contract), only the objects of TriviallyCopyable types are safe to access in the preserved part of the memory block after a call to realloc.


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 error has occurred. The pointer must be deallocated with Template:rlpf.


See also

C documentation for realloc