ALLOCA(3)               NetBSD Library Functions Manual              ALLOCA(3)

NAME
     alloca -- memory allocator

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdlib.h>

     void *
     alloca(size_t size);

DESCRIPTION
     The alloca() function allocates size bytes of space in the stack frame of
     the caller.  This temporary space is automatically freed on return.

RETURN VALUES
     The alloca() function returns a pointer to the beginning of the allocated
     space.  If the allocation failed, a NULL pointer is returned.

SEE ALSO
     brk(2), calloc(3), getpagesize(3), malloc(3), realloc(3)

CAVEATS
     Few limitations can be mentioned:

     ⊕   The alloca() function is machine dependent; its use is discouraged.

     ⊕   The alloca() function is slightly unsafe because it cannot ensure
         that the pointer returned points to a valid and usable block of mem-
         ory.  The allocation made may exceed the bounds of the stack, or even
         go further into other objects in memory, and alloca() cannot deter-
         mine such an error.  Avoid alloca() with large unbounded allocations.

     ⊕   Since alloca() modifies the stack at runtime, it causes problems to
         certain security features.  See security(7) for a discussion.

NetBSD 5.0                      March 21, 2011                      NetBSD 5.0