Commit | Line | Data |
---|---|---|
ffca4c22 | 1 | /* Safe automatic memory allocation. |
49114fd4 | 2 | Copyright (C) 2003-2007, 2009-2011 Free Software Foundation, Inc. |
ffca4c22 AW |
3 | Written by Bruno Haible <bruno@clisp.org>, 2003. |
4 | ||
5 | This program is free software; you can redistribute it and/or modify | |
6 | it under the terms of the GNU Lesser General Public License as published by | |
7 | the Free Software Foundation; either version 2, or (at your option) | |
8 | any later version. | |
9 | ||
10 | This program is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | GNU Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public License | |
16 | along with this program; if not, write to the Free Software Foundation, | |
17 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ | |
18 | ||
19 | #ifndef _MALLOCA_H | |
20 | #define _MALLOCA_H | |
21 | ||
22 | #include <alloca.h> | |
23 | #include <stddef.h> | |
24 | #include <stdlib.h> | |
25 | ||
26 | ||
27 | #ifdef __cplusplus | |
28 | extern "C" { | |
29 | #endif | |
30 | ||
31 | ||
32 | /* safe_alloca(N) is equivalent to alloca(N) when it is safe to call | |
33 | alloca(N); otherwise it returns NULL. It either returns N bytes of | |
34 | memory allocated on the stack, that lasts until the function returns, | |
35 | or NULL. | |
36 | Use of safe_alloca should be avoided: | |
37 | - inside arguments of function calls - undefined behaviour, | |
38 | - in inline functions - the allocation may actually last until the | |
39 | calling function returns. | |
40 | */ | |
41 | #if HAVE_ALLOCA | |
42 | /* The OS usually guarantees only one guard page at the bottom of the stack, | |
43 | and a page size can be as small as 4096 bytes. So we cannot safely | |
44 | allocate anything larger than 4096 bytes. Also care for the possibility | |
45 | of a few compiler-allocated temporary stack slots. | |
46 | This must be a macro, not an inline function. */ | |
47 | # define safe_alloca(N) ((N) < 4032 ? alloca (N) : NULL) | |
48 | #else | |
49 | # define safe_alloca(N) ((void) (N), NULL) | |
50 | #endif | |
51 | ||
52 | /* malloca(N) is a safe variant of alloca(N). It allocates N bytes of | |
53 | memory allocated on the stack, that must be freed using freea() before | |
54 | the function returns. Upon failure, it returns NULL. */ | |
55 | #if HAVE_ALLOCA | |
56 | # define malloca(N) \ | |
1cd4fffc | 57 | ((N) < 4032 - sa_increment \ |
ffca4c22 AW |
58 | ? (void *) ((char *) alloca ((N) + sa_increment) + sa_increment) \ |
59 | : mmalloca (N)) | |
60 | #else | |
61 | # define malloca(N) \ | |
62 | mmalloca (N) | |
63 | #endif | |
64 | extern void * mmalloca (size_t n); | |
65 | ||
66 | /* Free a block of memory allocated through malloca(). */ | |
67 | #if HAVE_ALLOCA | |
68 | extern void freea (void *p); | |
69 | #else | |
70 | # define freea free | |
71 | #endif | |
72 | ||
73 | /* nmalloca(N,S) is an overflow-safe variant of malloca (N * S). | |
74 | It allocates an array of N objects, each with S bytes of memory, | |
75 | on the stack. S must be positive and N must be nonnegative. | |
76 | The array must be freed using freea() before the function returns. */ | |
77 | #if 1 | |
78 | /* Cf. the definition of xalloc_oversized. */ | |
79 | # define nmalloca(n, s) \ | |
80 | ((n) > (size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) \ | |
81 | ? NULL \ | |
82 | : malloca ((n) * (s))) | |
83 | #else | |
84 | extern void * nmalloca (size_t n, size_t s); | |
85 | #endif | |
86 | ||
87 | ||
88 | #ifdef __cplusplus | |
89 | } | |
90 | #endif | |
91 | ||
92 | ||
93 | /* ------------------- Auxiliary, non-public definitions ------------------- */ | |
94 | ||
95 | /* Determine the alignment of a type at compile time. */ | |
96 | #if defined __GNUC__ | |
97 | # define sa_alignof __alignof__ | |
98 | #elif defined __cplusplus | |
99 | template <class type> struct sa_alignof_helper { char __slot1; type __slot2; }; | |
100 | # define sa_alignof(type) offsetof (sa_alignof_helper<type>, __slot2) | |
101 | #elif defined __hpux | |
102 | /* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof | |
103 | values. */ | |
104 | # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8) | |
105 | #elif defined _AIX | |
106 | /* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof | |
107 | values. */ | |
108 | # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8) | |
109 | #else | |
110 | # define sa_alignof(type) offsetof (struct { char __slot1; type __slot2; }, __slot2) | |
111 | #endif | |
112 | ||
113 | enum | |
114 | { | |
115 | /* The desired alignment of memory allocations is the maximum alignment | |
116 | among all elementary types. */ | |
117 | sa_alignment_long = sa_alignof (long), | |
118 | sa_alignment_double = sa_alignof (double), | |
119 | #if HAVE_LONG_LONG_INT | |
120 | sa_alignment_longlong = sa_alignof (long long), | |
121 | #endif | |
122 | sa_alignment_longdouble = sa_alignof (long double), | |
123 | sa_alignment_max = ((sa_alignment_long - 1) | (sa_alignment_double - 1) | |
124 | #if HAVE_LONG_LONG_INT | |
1cd4fffc | 125 | | (sa_alignment_longlong - 1) |
ffca4c22 | 126 | #endif |
1cd4fffc LC |
127 | | (sa_alignment_longdouble - 1) |
128 | ) + 1, | |
ffca4c22 AW |
129 | /* The increment that guarantees room for a magic word must be >= sizeof (int) |
130 | and a multiple of sa_alignment_max. */ | |
131 | sa_increment = ((sizeof (int) + sa_alignment_max - 1) / sa_alignment_max) * sa_alignment_max | |
132 | }; | |
133 | ||
134 | #endif /* _MALLOCA_H */ |