void *realloc(void *ptr, size_t size);
IEEE Std 1003.1-2017
realloc() function shall deallocate the old object pointed to by ptr and return a pointer to a new object that
has the size specified by size. The contents of the new object shall be the same as that of the old object prior to
deallocation, up to the lesser of the new and old sizes. Any bytes in the new object beyond the size of the old object have
indeterminate values. If the size of the space requested is zero, the behavior shall be implementation-defined: either a
pointer is returned, or the behavior shall be as if the size were some non-zero value, except that the behavior is undefined if the
returned pointer is used to access an object. If the space cannot be allocated, the object shall remain unchanged.
If ptr is a
realloc() shall be equivalent to
for the specified size.
If ptr does not match a pointer returned earlier by
realloc() or if the space has previously been deallocated by a call to
realloc(), the behavior is undefined.
The order and contiguity of storage allocated by successive calls to
realloc() is unspecified. The pointer returned if
the allocation succeeds shall be suitably aligned so that it may be assigned to a pointer to any type of object and then used to
access such an object in the space allocated (until the space is explicitly freed or reallocated). Each such allocation shall yield
a pointer to an object disjoint from any other object. The pointer returned shall point to the start (lowest byte address) of the
allocated space. If the space cannot be allocated, a
null pointer shall be returned.
Upon successful completion,
realloc() shall return a pointer to the (possibly moved) allocated space. If size is
nullpointer shall be returned and, if ptr is not a
nullpointer, errno shall be set to an implementation-defined value.
A pointer to the allocated space shall be returned, and the memory object pointed to by ptr shall be freed. The application shall ensure that the pointer is not used to access an object.
If there is not enough available memory,
realloc() shall return a
null pointer and set
realloc() returns a
errno has been set to
memory referenced by ptr shall not be changed.
realloc() function shall fail if:
ENOMEM- Insufficient memory is available.