This function changes the size of a previously allocated block of task memory.
The pv argument points to the beginning of the memory block. If pv is NULL, CoTaskMemRealloc allocates a new memory block in the same way as the CoTaskMemAlloc function. If pv is not NULL, it should be a pointer returned by a prior call to CoTaskMemAlloc.
The cb argument specifies the size (in bytes) of the new block. The contents of the block are unchanged up to the shorter of the new and old sizes, although the new block can be in a different location. Because the new block can be in a different memory location, the pointer returned by CoTaskMemRealloc is not guaranteed to be the pointer passed through the pv argument. If pv is not NULL and cb is zero, then the memory pointed to by pv is freed.
CoTaskMemRealloc returns a void pointer to the reallocated (and possibly moved) memory block. The return value is NULL if the size is zero and the buffer argument is not NULL, or if there is not enough memory available to expand the block to the given size. In the first case, the original block is freed; in the second, the original block is unchanged.
The storage space pointed to by the return value is guaranteed to be 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.
Passing into this function any invalid and, under some circumstances, NULL pointers result in unexpected termination of the application.
To determine whether the platform supports this function, see Determining Supported COM APIs.