cce09a6cbb66b0474d25dabcf34a43e3728f71ef
[lttng-tools.git] / src / common / macros.h
1 /*
2 * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
3 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 *
5 * SPDX-License-Identifier: GPL-2.0-only
6 *
7 */
8
9 #ifndef _MACROS_H
10 #define _MACROS_H
11
12 #include <stdlib.h>
13 #include <stddef.h>
14 #include <string.h>
15 #include <common/compat/string.h>
16
17 /*
18 * Takes a pointer x and transform it so we can use it to access members
19 * without a function call. Here an example:
20 *
21 * #define GET_SIZE(x) LTTNG_REF(x)->size
22 *
23 * struct { int size; } s;
24 *
25 * printf("size : %d\n", GET_SIZE(&s));
26 *
27 * For this example we can't use something like this for compatibility purpose
28 * since this will fail:
29 *
30 * #define GET_SIZE(x) x->size;
31 *
32 * This is mostly use for the compatibility layer of lttng-tools. See
33 * poll/epoll for a good example. Since x can be on the stack or allocated
34 * memory using malloc(), we must use generic accessors for compat in order to
35 * *not* use a function to access members and not the variable name.
36 */
37 #define LTTNG_REF(x) ((typeof(*x) *)(x))
38
39 /*
40 * Memory allocation zeroed
41 */
42 static inline
43 void *zmalloc(size_t len)
44 {
45 return calloc(1, len);
46 }
47
48 #ifndef ARRAY_SIZE
49 #define ARRAY_SIZE(array) (sizeof(array) / (sizeof((array)[0])))
50 #endif
51
52 #ifndef container_of
53 #define container_of(ptr, type, member) \
54 ({ \
55 const typeof(((type *)NULL)->member) * __ptr = (ptr); \
56 (type *)((char *)__ptr - offsetof(type, member)); \
57 })
58 #endif
59
60 #ifndef max
61 #define max(a, b) ((a) > (b) ? (a) : (b))
62 #endif
63
64 #ifndef max_t
65 #define max_t(type, a, b) max((type) a, (type) b)
66 #endif
67
68 #ifndef min
69 #define min(a, b) ((a) < (b) ? (a) : (b))
70 #endif
71
72 #ifndef min_t
73 #define min_t(type, a, b) min((type) a, (type) b)
74 #endif
75
76 #ifndef LTTNG_PACKED
77 #define LTTNG_PACKED __attribute__((__packed__))
78 #endif
79
80 #define is_signed(type) (((type) (-1)) < 0)
81
82 /*
83 * Align value to the next multiple of align. Returns val if it already is a
84 * multiple of align. Align must be a power of two.
85 */
86 #define ALIGN_TO(value, align) ((value + (align - 1)) & ~(align - 1))
87
88 /*
89 * LTTNG_HIDDEN: set the hidden attribute for internal functions
90 * On Windows, symbols are local unless explicitly exported,
91 * see https://gcc.gnu.org/wiki/Visibility
92 */
93 #if defined(_WIN32) || defined(__CYGWIN__)
94 #define LTTNG_HIDDEN
95 #else
96 #define LTTNG_HIDDEN __attribute__((visibility("hidden")))
97 #endif
98
99 #define member_sizeof(type, field) sizeof(((type *) 0)->field)
100
101 #define ASSERT_LOCKED(lock) assert(pthread_mutex_trylock(&lock))
102
103 /*
104 * Get an aligned pointer to a value. This is meant
105 * as a helper to pass an aligned pointer to a member in a packed structure
106 * to a function.
107 */
108 #define ALIGNED_CONST_PTR(value) (((const typeof(value) []) { value }))
109
110 /*
111 * lttng_strncpy returns 0 on success, or nonzero on failure.
112 * It checks that the @src string fits into @dst_len before performing
113 * the copy. On failure, no copy has been performed.
114 *
115 * dst_len includes the string's trailing NULL.
116 */
117 static inline
118 int lttng_strncpy(char *dst, const char *src, size_t dst_len)
119 {
120 if (lttng_strnlen(src, dst_len) >= dst_len) {
121 /* Fail since copying would result in truncation. */
122 return -1;
123 }
124 strcpy(dst, src);
125 return 0;
126 }
127
128 #endif /* _MACROS_H */
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