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32 .\" @(#)alloca.3 5.1 (Berkeley) 5/2/91
34 .\" Converted Mon Nov 29 11:05:55 1993 by Rik Faith <faith@cs.unc.edu>
35 .\" Modified Tue Oct 22 23:41:56 1996 by Eric S. Raymond <esr@thyrsus.com>
36 .\" Modified 2002-07-17, aeb
38 .TH ALLOCA 3 2002-07-17 "GNU" "Linux Programmer's Manual"
40 alloca \- memory allocator
42 .B #include <alloca.h>
44 .BI "void *alloca(size_t " size );
50 bytes of space in the stack frame of the caller.
51 This temporary space is
52 automatically freed when the function that called
54 returns to its caller.
58 function returns a pointer to the beginning of the allocated space.
59 If the allocation causes stack overflow, program behaviour is undefined.
61 There is evidence that the
63 function appeared in 32v, pwb, pwb.2, 3bsd, and 4bsd.
64 There is a man page for it in 4.3BSD.
65 Linux uses the GNU version.
66 This function is not in POSIX.1-2001.
68 .SS Notes on the GNU Version
74 This is not done when either the \-ansi or
75 the \-fno\-builtin option is given.
77 By default the glibc version of
81 and that contains the line:
84 # define alloca(size) __builtin_alloca (size)
87 with messy consequences if one has a private version of this function.
89 The fact that the code is inlined, means that it is impossible
90 to take the address of this function, or to change its behaviour
91 by linking with a different library.
93 The inlined code often consists of a single instruction adjusting
94 the stack pointer, and does not check for stack overflow.
95 Thus, there is no NULL error return.
99 function is machine and compiler dependent.
101 its implementation is buggy.
102 Its use is discouraged.
106 cannot be used inside the list of arguments of a function call, because
107 the stack space reserved by
109 would appear on the stack in the middle of the space for the