ALLOCA(3) Library Functions Manual ALLOCA(3)

alloca
memory allocator

Standard C Library (libc, -lc)

#include <stdlib.h>

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.

cc(1), brk(2), calloc(3), getpagesize(3), malloc(3), realloc(3), security(7)

Few limitations can be mentioned:
October 24, 2012 NetBSD 9.2