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ALLOCA(3)		   Linux Programmer's Manual		     ALLOCA(3)

NAME
       alloca -	memory allocator

SYNOPSIS
       #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 func-
       tion that called	alloca returns to its caller.

RETURN VALUE
       The alloca function returns a pointer to	the beginning of the allocated
       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 BSD 4.3.	Linux uses the
       GNU version.  This function is not in POSIX or SUSv3.

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	_stdlib.h_ includes _alloca.h_
       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 systems
       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	arguments.

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

GNU				  2002-07-17			     ALLOCA(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES ON THE GNU VERSION | BUGS | SEE ALSO

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