dhcpd-pools  2.28
ISC dhcpd lease usage analyser
malloca.h
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1 /* Safe automatic memory allocation.
2  Copyright (C) 2003-2007, 2009-2015 Free Software Foundation, Inc.
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 General Public License as published by
7  the Free Software Foundation; either version 3, 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 General Public License for more details.
14 
15  You should have received a copy of the GNU General Public License
16  along with this program; if not, see <http://www.gnu.org/licenses/>. */
17 
18 #ifndef _MALLOCA_H
19 #define _MALLOCA_H
20 
21 #include <alloca.h>
22 #include <stddef.h>
23 #include <stdlib.h>
24 
25 
26 #ifdef __cplusplus
27 extern "C" {
28 #endif
29 
30 
31 /* safe_alloca(N) is equivalent to alloca(N) when it is safe to call
32  alloca(N); otherwise it returns NULL. It either returns N bytes of
33  memory allocated on the stack, that lasts until the function returns,
34  or NULL.
35  Use of safe_alloca should be avoided:
36  - inside arguments of function calls - undefined behaviour,
37  - in inline functions - the allocation may actually last until the
38  calling function returns.
39 */
40 #if HAVE_ALLOCA
41 /* The OS usually guarantees only one guard page at the bottom of the stack,
42  and a page size can be as small as 4096 bytes. So we cannot safely
43  allocate anything larger than 4096 bytes. Also care for the possibility
44  of a few compiler-allocated temporary stack slots.
45  This must be a macro, not a function. */
46 # define safe_alloca(N) ((N) < 4032 ? alloca (N) : NULL)
47 #else
48 # define safe_alloca(N) ((void) (N), NULL)
49 #endif
50 
51 /* malloca(N) is a safe variant of alloca(N). It allocates N bytes of
52  memory allocated on the stack, that must be freed using freea() before
53  the function returns. Upon failure, it returns NULL. */
54 #if HAVE_ALLOCA
55 # define malloca(N) \
56  ((N) < 4032 - sa_increment \
57  ? (void *) ((char *) alloca ((N) + sa_increment) + sa_increment) \
58  : mmalloca (N))
59 #else
60 # define malloca(N) \
61  mmalloca (N)
62 #endif
63 extern void * mmalloca (size_t n);
64 
65 /* Free a block of memory allocated through malloca(). */
66 #if HAVE_ALLOCA
67 extern void freea (void *p);
68 #else
69 # define freea free
70 #endif
71 
72 /* nmalloca(N,S) is an overflow-safe variant of malloca (N * S).
73  It allocates an array of N objects, each with S bytes of memory,
74  on the stack. S must be positive and N must be nonnegative.
75  The array must be freed using freea() before the function returns. */
76 #if 1
77 /* Cf. the definition of xalloc_oversized. */
78 # define nmalloca(n, s) \
79  ((n) > (size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) \
80  ? NULL \
81  : malloca ((n) * (s)))
82 #else
83 extern void * nmalloca (size_t n, size_t s);
84 #endif
85 
86 
87 #ifdef __cplusplus
88 }
89 #endif
90 
91 
92 /* ------------------- Auxiliary, non-public definitions ------------------- */
93 
94 /* Determine the alignment of a type at compile time. */
95 #if defined __GNUC__ || defined __IBM__ALIGNOF__
96 # define sa_alignof __alignof__
97 #elif defined __cplusplus
98  template <class type> struct sa_alignof_helper { char __slot1; type __slot2; };
99 # define sa_alignof(type) offsetof (sa_alignof_helper<type>, __slot2)
100 #elif defined __hpux
101  /* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof
102  values. */
103 # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
104 #elif defined _AIX
105  /* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof
106  values. */
107 # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
108 #else
109 # define sa_alignof(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
110 #endif
111 
112 enum
113 {
114 /* The desired alignment of memory allocations is the maximum alignment
115  among all elementary types. */
118 #if HAVE_LONG_LONG_INT
119  sa_alignment_longlong = sa_alignof (long long),
120 #endif
123 #if HAVE_LONG_LONG_INT
124  | (sa_alignment_longlong - 1)
125 #endif
127  ) + 1,
128 /* The increment that guarantees room for a magic word must be >= sizeof (int)
129  and a multiple of sa_alignment_max. */
131 };
132 
133 #endif /* _MALLOCA_H */
void * mmalloca(size_t n)
Definition: malloca.c:74
Definition: malloca.h:116
#define nmalloca(n, s)
Definition: malloca.h:78
Definition: malloca.h:121
Definition: malloca.h:130
Definition: malloca.h:117
Definition: malloca.h:122
#define freea
Definition: malloca.h:69
#define sa_alignof(type)
Definition: malloca.h:109