alloca – memory allocator

USAGE
       #include <alloca.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  when  the
       function that called alloca() returns to its caller.

RETURN VALUE
       The  alloca()  function returns a pointer to the beginning of the allo-
       cated  space.   If  the  allocation  causes  stack  overflow,   program
       behaviour is undefined.

CONFORMING TO
       There  is  evidence  that  the  alloca() function appeared in 32v, pwb,
       pwb.2, 3bsd, and 4bsd.  There is a man page for it  in  4.3BSD.   Linux
       uses the GNU version.  This function is not in POSIX.1-2001.

NOTES ON THE GNU VERSION
       Normally, gcc translates calls to alloca() by inlined code. This is not
       done when either the -ansi or the -fno-builtin  option  is  given.  But
       beware!  By default the glibc version of  includes
       and that contains the line
              # define alloca(size)   __builtin_alloca (size)
       with messy consequences if one has a private version of this  function.

       The  fact that the code is inlined, means that it is impossible to take
       the address of this function, or to change  its  behaviour  by  linking
       with a different library.

       The  inlined  code often consists of a single instruction adjusting the
       stack pointer, and does not check for stack overflow.  Thus,  there  is
       no NULL error return.

BUGS
       The  alloca()  function is machine and compiler dependent. On many sys-
       tems its implementation is buggy. Its use is discouraged.

       On many systems alloca() cannot be used inside the list of arguments of
       a  function  call,  because  the stack space reserved by alloca() would
       appear on the stack in the middle of the space for the  function  argu-
       ments.

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