alloca − memory allocator
void *alloca( size_t size);
The alloca function allocates size bytes of space in the stack frame of the caller. This temporary space is automatically freed on return.
The alloca function returns a pointer to the beginning of the allocated space. If the allocation failed, a NULL pointer is returned.
There is evidence that the alloca function appeared in 32v, pwb, pwb.2, 3bsd, and 4bsd. There is a man page for it in BSD 4.3. Linux uses the GNU version.
The alloca function is machine dependent.