1/* GLIB - Library of useful routines for C programming
2 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18/*
19 * Modified by the GLib Team and others 1997-2000. See the AUTHORS
20 * file for a list of people on the GLib Team. See the ChangeLog
21 * files for a list of changes. These files are distributed with
22 * GLib at ftp://ftp.gtk.org/pub/gtk/.
23 */
24
25#ifndef __G_ALLOCA_H__
26#define __G_ALLOCA_H__
27
28#if !defined (__GLIB_H_INSIDE__) && !defined (GLIB_COMPILATION)
29#error "Only <glib.h> can be included directly."
30#endif
31
32#include <glib/gtypes.h>
33
34#if defined(__BIONIC__) && defined (GLIB_HAVE_ALLOCA_H)
35# include <alloca.h>
36#elif defined(__GNUC__)
37/* GCC does the right thing */
38# undef alloca
39# define alloca(size) __builtin_alloca (size)
40#elif defined (GLIB_HAVE_ALLOCA_H)
41/* a native and working alloca.h is there */
42# include <alloca.h>
43#else /* !__GNUC__ && !GLIB_HAVE_ALLOCA_H */
44# if defined(_MSC_VER) || defined(__DMC__)
45# include <malloc.h>
46# define alloca _alloca
47# else /* !_MSC_VER && !__DMC__ */
48# ifdef _AIX
49# pragma alloca
50# else /* !_AIX */
51# ifndef alloca /* predefined by HP cc +Olibcalls */
52G_BEGIN_DECLS
53char *alloca ();
54G_END_DECLS
55# endif /* !alloca */
56# endif /* !_AIX */
57# endif /* !_MSC_VER && !__DMC__ */
58#endif /* !__GNUC__ && !GLIB_HAVE_ALLOCA_H */
59
60/**
61 * g_alloca:
62 * @size: number of bytes to allocate.
63 *
64 * Allocates @size bytes on the stack; these bytes will be freed when the current
65 * stack frame is cleaned up. This macro essentially just wraps the alloca()
66 * function present on most UNIX variants.
67 * Thus it provides the same advantages and pitfalls as alloca():
68 *
69 * - alloca() is very fast, as on most systems it's implemented by just adjusting
70 * the stack pointer register.
71 *
72 * - It doesn't cause any memory fragmentation, within its scope, separate alloca()
73 * blocks just build up and are released together at function end.
74 *
75 * - Allocation sizes have to fit into the current stack frame. For instance in a
76 * threaded environment on Linux, the per-thread stack size is limited to 2 Megabytes,
77 * so be sparse with alloca() uses.
78 *
79 * - Allocation failure due to insufficient stack space is not indicated with a %NULL
80 * return like e.g. with malloc(). Instead, most systems probably handle it the same
81 * way as out of stack space situations from infinite function recursion, i.e.
82 * with a segmentation fault.
83 *
84 * - Special care has to be taken when mixing alloca() with GNU C variable sized arrays.
85 * Stack space allocated with alloca() in the same scope as a variable sized array
86 * will be freed together with the variable sized array upon exit of that scope, and
87 * not upon exit of the enclosing function scope.
88 *
89 * Returns: space for @size bytes, allocated on the stack
90 */
91#define g_alloca(size) alloca (size)
92/**
93 * g_newa:
94 * @struct_type: Type of memory chunks to be allocated
95 * @n_structs: Number of chunks to be allocated
96 *
97 * Wraps g_alloca() in a more typesafe manner.
98 *
99 * Returns: Pointer to stack space for @n_structs chunks of type @struct_type
100 */
101#define g_newa(struct_type, n_structs) ((struct_type*) g_alloca (sizeof (struct_type) * (gsize) (n_structs)))
102
103#endif /* __G_ALLOCA_H__ */
104