1 | /* GLIB - Library of useful routines for C programming |
2 | * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald |
3 | * |
4 | * SPDX-License-Identifier: LGPL-2.1-or-later |
5 | * |
6 | * This library is free software; you can redistribute it and/or |
7 | * modify it under the terms of the GNU Lesser General Public |
8 | * License as published by the Free Software Foundation; either |
9 | * version 2.1 of the License, or (at your option) any later version. |
10 | * |
11 | * This library is distributed in the hope that it will be useful, |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | * Lesser General Public License for more details. |
15 | * |
16 | * You should have received a copy of the GNU Lesser General Public |
17 | * License along with this library; if not, see <http://www.gnu.org/licenses/>. |
18 | */ |
19 | |
20 | /* |
21 | * Modified by the GLib Team and others 1997-2000. See the AUTHORS |
22 | * file for a list of people on the GLib Team. See the ChangeLog |
23 | * files for a list of changes. These files are distributed with |
24 | * GLib at ftp://ftp.gtk.org/pub/gtk/. |
25 | */ |
26 | |
27 | #ifndef __G_ALLOCA_H__ |
28 | #define __G_ALLOCA_H__ |
29 | |
30 | #if !defined (__GLIB_H_INSIDE__) && !defined (GLIB_COMPILATION) |
31 | #error "Only <glib.h> can be included directly." |
32 | #endif |
33 | |
34 | #include <glib/gtypes.h> |
35 | #include <string.h> |
36 | |
37 | #if defined(__BIONIC__) && defined (GLIB_HAVE_ALLOCA_H) |
38 | # include <alloca.h> |
39 | #elif defined(__GNUC__) |
40 | /* GCC does the right thing */ |
41 | # undef alloca |
42 | # define alloca(size) __builtin_alloca (size) |
43 | #elif defined (GLIB_HAVE_ALLOCA_H) |
44 | /* a native and working alloca.h is there */ |
45 | # include <alloca.h> |
46 | #else /* !__GNUC__ && !GLIB_HAVE_ALLOCA_H */ |
47 | # if defined(_MSC_VER) || defined(__DMC__) |
48 | # include <malloc.h> |
49 | # define alloca _alloca |
50 | # else /* !_MSC_VER && !__DMC__ */ |
51 | # ifdef _AIX |
52 | # pragma alloca |
53 | # else /* !_AIX */ |
54 | # ifndef alloca /* predefined by HP cc +Olibcalls */ |
55 | G_BEGIN_DECLS |
56 | char *alloca (); |
57 | G_END_DECLS |
58 | # endif /* !alloca */ |
59 | # endif /* !_AIX */ |
60 | # endif /* !_MSC_VER && !__DMC__ */ |
61 | #endif /* !__GNUC__ && !GLIB_HAVE_ALLOCA_H */ |
62 | |
63 | /** |
64 | * g_alloca: |
65 | * @size: number of bytes to allocate. |
66 | * |
67 | * Allocates @size bytes on the stack; these bytes will be freed when the current |
68 | * stack frame is cleaned up. This macro essentially just wraps the alloca() |
69 | * function present on most UNIX variants. |
70 | * Thus it provides the same advantages and pitfalls as alloca(): |
71 | * |
72 | * - alloca() is very fast, as on most systems it's implemented by just adjusting |
73 | * the stack pointer register. |
74 | * |
75 | * - It doesn't cause any memory fragmentation, within its scope, separate alloca() |
76 | * blocks just build up and are released together at function end. |
77 | * |
78 | * - Allocation sizes have to fit into the current stack frame. For instance in a |
79 | * threaded environment on Linux, the per-thread stack size is limited to 2 Megabytes, |
80 | * so be sparse with alloca() uses. |
81 | * |
82 | * - Allocation failure due to insufficient stack space is not indicated with a %NULL |
83 | * return like e.g. with malloc(). Instead, most systems probably handle it the same |
84 | * way as out of stack space situations from infinite function recursion, i.e. |
85 | * with a segmentation fault. |
86 | * |
87 | * - Allowing @size to be specified by an untrusted party would allow for them |
88 | * to trigger a segmentation fault by specifying a large size, leading to a |
89 | * denial of service vulnerability. @size must always be entirely under the |
90 | * control of the program. |
91 | * |
92 | * - Special care has to be taken when mixing alloca() with GNU C variable sized arrays. |
93 | * Stack space allocated with alloca() in the same scope as a variable sized array |
94 | * will be freed together with the variable sized array upon exit of that scope, and |
95 | * not upon exit of the enclosing function scope. |
96 | * |
97 | * Returns: space for @size bytes, allocated on the stack |
98 | */ |
99 | #define g_alloca(size) alloca (size) |
100 | |
101 | /** |
102 | * g_alloca0: |
103 | * @size: number of bytes to allocate. |
104 | * |
105 | * Wraps g_alloca() and initializes allocated memory to zeroes. |
106 | * If @size is `0` it returns %NULL. |
107 | * |
108 | * Note that the @size argument will be evaluated multiple times. |
109 | * |
110 | * Returns: (nullable) (transfer full): space for @size bytes, allocated on the stack |
111 | * |
112 | * Since: 2.72 |
113 | */ |
114 | #define g_alloca0(size) ((size) == 0 ? NULL : memset (g_alloca (size), 0, (size))) |
115 | |
116 | /** |
117 | * g_newa: |
118 | * @struct_type: Type of memory chunks to be allocated |
119 | * @n_structs: Number of chunks to be allocated |
120 | * |
121 | * Wraps g_alloca() in a more typesafe manner. |
122 | * |
123 | * As mentioned in the documentation for g_alloca(), @n_structs must always be |
124 | * entirely under the control of the program, or you may introduce a denial of |
125 | * service vulnerability. In addition, the multiplication of @struct_type by |
126 | * @n_structs is not checked, so an overflow may lead to a remote code execution |
127 | * vulnerability. |
128 | * |
129 | * Returns: Pointer to stack space for @n_structs chunks of type @struct_type |
130 | */ |
131 | #define g_newa(struct_type, n_structs) ((struct_type*) g_alloca (sizeof (struct_type) * (gsize) (n_structs))) |
132 | |
133 | /** |
134 | * g_newa0: |
135 | * @struct_type: the type of the elements to allocate. |
136 | * @n_structs: the number of elements to allocate. |
137 | * |
138 | * Wraps g_alloca0() in a more typesafe manner. |
139 | * |
140 | * Returns: (nullable) (transfer full): Pointer to stack space for @n_structs |
141 | * chunks of type @struct_type |
142 | * |
143 | * Since: 2.72 |
144 | */ |
145 | #define g_newa0(struct_type, n_structs) ((struct_type*) g_alloca0 (sizeof (struct_type) * (gsize) (n_structs))) |
146 | |
147 | #endif /* __G_ALLOCA_H__ */ |
148 | |