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 /*
  81  * Align value to the next multiple of align. Returns val if it already is a
  82  * multiple of align. Align must be a power of two.
  83  */
  84 #define ALIGN_TO(value, align) ((value + (align - 1)) & ~(align - 1))
  85
  86 /*
  87  * LTTNG_HIDDEN: set the hidden attribute for internal functions
  88  * On Windows, symbols are local unless explicitly exported,
  89  * see https://gcc.gnu.org/wiki/Visibility
  90  */
  91 #if defined(_WIN32) || defined(__CYGWIN__)
  92 #define LTTNG_HIDDEN
  93 #else
  94 #define LTTNG_HIDDEN __attribute__((visibility("hidden")))
  95 #endif
  96
  97 #define member_sizeof(type, field)      sizeof(((type *) 0)->field)
  98
  99 #define ASSERT_LOCKED(lock) assert(pthread_mutex_trylock(&lock))
 100
 101 /*
 102  * Get an aligned pointer to a value. This is meant
 103  * as a helper to pass an aligned pointer to a member in a packed structure
 104  * to a function.
 105  */
 106 #define ALIGNED_CONST_PTR(value) (((const typeof(value) []) { value }))
 107
 108 /*
 109  * lttng_strncpy returns 0 on success, or nonzero on failure.
 110  * It checks that the @src string fits into @dst_len before performing
 111  * the copy. On failure, no copy has been performed.
 112  *
 113  * dst_len includes the string's trailing NULL.
 114  */
 115 static inline
 116 int lttng_strncpy(char *dst, const char *src, size_t dst_len)
 117 {
 118         if (lttng_strnlen(src, dst_len) >= dst_len) {
 119                 /* Fail since copying would result in truncation. */
 120                 return -1;
 121         }
 122         strcpy(dst, src);
 123         return 0;
 124 }
 125
 126 #endif /* _MACROS_H */