Fix undefined NULL pointer arithmetic
[urcu.git] / urcu-pointer.h
1 #ifndef _URCU_POINTER_H
2 #define _URCU_POINTER_H
3
4 /*
5 * urcu-pointer.h
6 *
7 * Userspace RCU header. Operations on pointers.
8 *
9 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
11 *
12 * This library is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU Lesser General Public
14 * License as published by the Free Software Foundation; either
15 * version 2.1 of the License, or (at your option) any later version.
16 *
17 * This library is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * Lesser General Public License for more details.
21 *
22 * You should have received a copy of the GNU Lesser General Public
23 * License along with this library; if not, write to the Free Software
24 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 *
26 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
27 */
28
29 #include <urcu/compiler.h>
30 #include <urcu/arch.h>
31 #include <urcu/uatomic.h>
32
33 #ifdef __cplusplus
34 extern "C" {
35 #endif
36
37 #if defined(_LGPL_SOURCE) || defined(URCU_INLINE_SMALL_FUNCTIONS)
38
39 #include <urcu/static/urcu-pointer.h>
40
41 /*
42 * rcu_dereference(ptr)
43 *
44 * Fetch a RCU-protected pointer. Typically used to copy the variable ptr to a
45 * local variable.
46 */
47 #define rcu_dereference _rcu_dereference
48
49 /*
50 * type *rcu_cmpxchg_pointer(type **ptr, type *new, type *old)
51 * type *rcu_xchg_pointer(type **ptr, type *new)
52 * void rcu_set_pointer(type **ptr, type *new)
53 *
54 * RCU pointer updates.
55 * @ptr: address of the pointer to modify
56 * @new: new pointer value
57 * @old: old pointer value (expected)
58 *
59 * return: old pointer value
60 */
61 #define rcu_cmpxchg_pointer _rcu_cmpxchg_pointer
62 #define rcu_xchg_pointer _rcu_xchg_pointer
63 #define rcu_set_pointer _rcu_set_pointer
64
65 #else /* !(defined(_LGPL_SOURCE) || defined(URCU_INLINE_SMALL_FUNCTIONS)) */
66
67 extern void *rcu_dereference_sym(void *p);
68 #define rcu_dereference(p) \
69 ({ \
70 __typeof__(p) _________p1 = URCU_FORCE_CAST(__typeof__(p), \
71 rcu_dereference_sym(URCU_FORCE_CAST(void *, p))); \
72 (_________p1); \
73 })
74
75 extern void *rcu_cmpxchg_pointer_sym(void **p, void *old, void *_new);
76 #define rcu_cmpxchg_pointer(p, old, _new) \
77 ({ \
78 __typeof__(*(p)) _________pold = (old); \
79 __typeof__(*(p)) _________pnew = (_new); \
80 __typeof__(*(p)) _________p1 = URCU_FORCE_CAST(__typeof__(*(p)), \
81 rcu_cmpxchg_pointer_sym(URCU_FORCE_CAST(void **, p), \
82 _________pold, \
83 _________pnew)); \
84 (_________p1); \
85 })
86
87 extern void *rcu_xchg_pointer_sym(void **p, void *v);
88 #define rcu_xchg_pointer(p, v) \
89 ({ \
90 __typeof__(*(p)) _________pv = (v); \
91 __typeof__(*(p)) _________p1 = URCU_FORCE_CAST(__typeof__(*(p)), \
92 rcu_xchg_pointer_sym(URCU_FORCE_CAST(void **, p), \
93 _________pv)); \
94 (_________p1); \
95 })
96
97 /*
98 * Note: rcu_set_pointer_sym returns @v because we don't want to break
99 * the ABI. At the API level, rcu_set_pointer() now returns void. Use of
100 * the return value is therefore deprecated, and will cause a build
101 * error.
102 */
103 extern void *rcu_set_pointer_sym(void **p, void *v);
104 #define rcu_set_pointer(p, v) \
105 do { \
106 __typeof__(*(p)) _________pv = (v); \
107 (void) rcu_set_pointer_sym(URCU_FORCE_CAST(void **, p), \
108 _________pv); \
109 } while (0)
110
111 #endif /* !(defined(_LGPL_SOURCE) || defined(URCU_INLINE_SMALL_FUNCTIONS)) */
112
113 /*
114 * void rcu_assign_pointer(type *ptr, type *new)
115 *
116 * Same as rcu_set_pointer, but takes the pointer to assign to rather than its
117 * address as first parameter. Provided for compatibility with the Linux kernel
118 * RCU semantic.
119 */
120 #define rcu_assign_pointer(p, v) rcu_set_pointer((&p), (v))
121
122 #ifdef __cplusplus
123 }
124 #endif
125
126 #endif /* _URCU_POINTER_H */
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