Changes the size of the area pointed to by the first argument to the number of bytes given by the second argument. These functions are AST-reentrant.
#include <stdlib.h> void *realloc (void *ptr, size_t size);Function Variants This function also has variants named _realloc32 and _realloc64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.8 for more information on using pointer-size-specific functions.
The contents of the area are unchanged up to the lesser of the old and new sizes. The ANSI C Standard states that "If the new size is larger than the old size, the value of the newly allocated portion of memory is indeterminate." For compatibility with old implementations, DEC C initializes the newly allocated memory to 0.
For efficiency, the previous actual allocation could have been larger than the requested size. If it was allocated with malloc, the value of the portion of memory between the previous requested allocation and the actual allocation is indeterminate. If it was allocated with calloc, that same memory was initialized to 0. If your application relies on realloc initializing memory to 0, then use calloc instead of malloc to perform the initial allocation.
See also free, cfree, calloc, and malloc in this section.
| x | The address of the area, quadword- aligned. The address is returned because the area may have to be moved to a new address to reallocate enough space. If the area was moved, the space previously occupied is freed. |
| NULL | Indicates that space cannot be reallocated (for example, if there is not enough room). |