src/common/macros.h

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  */
   6
   7 #ifndef _BABELTRACE_INTERNAL_H
   8 #define _BABELTRACE_INTERNAL_H
   9
  10 #ifdef __cplusplus
  11 extern "C" {
  12 #endif
  13
  14 #ifdef __cplusplus
  15 #define BT_EXTERN_C extern "C"
  16 #else
  17 #define BT_EXTERN_C
  18 #endif
  19
  20 #define bt_max_t(type, a, b)    \
  21         ((type) (a) > (type) (b) ? (type) (a) : (type) (b))
  22
  23 /*
  24  * BT_EXPORT: set the visibility for exported functions.
  25  */
  26 #if defined(_WIN32) || defined(__CYGWIN__)
  27 #define BT_EXPORT
  28 #else
  29 #define BT_EXPORT __attribute__((visibility("default")))
  30 #endif
  31
  32 /*
  33  * BT_NOEXCEPT: defined to `noexcept` if compiling as C++, else empty.
  34  */
  35 #if defined(__cplusplus)
  36 #define BT_NOEXCEPT noexcept
  37 #else
  38 #define BT_NOEXCEPT
  39 #endif
  40
  41 /* Enable `txt` if developer mode is enabled. */
  42 #ifdef BT_DEV_MODE
  43 #define BT_IF_DEV_MODE(txt) txt
  44 #else
  45 #define BT_IF_DEV_MODE(txt)
  46 #endif
  47
  48 /*
  49  * Yield `ref`'s value while setting `ref` to NULL.
  50  *
  51  * This can be used to give a strong reference to a callee:
  52  *
  53  *   add_foo_to_list(list, BT_MOVE_REF(foo));
  54  *
  55  * or in a simple assignment:
  56  *
  57  *   my_struct->foo = BT_MOVE_REF(foo);
  58  *
  59  * When moving a reference in a function call, the reference is given to the
  60  * callee even if that function call fails, so make sure the called function
  61  * is written accordingly.
  62  */
  63
  64 #define BT_MOVE_REF(ref)                \
  65         ({                              \
  66                 __typeof__(ref) _ref = ref;     \
  67                 ref = NULL;             \
  68                 _ref;                   \
  69         })
  70
  71 /* Wrapper for g_array_index that adds bound checking.  */
  72 #define bt_g_array_index(a, t, i)               \
  73         g_array_index((a), t, ({ BT_ASSERT_DBG((i) < (a)->len); (i); }))
  74
  75 /*
  76  * Copied from:
  77  * <https://stackoverflow.com/questions/37411809/how-to-elegantly-fix-this-unused-variable-warning/37412551#37412551>:
  78  *
  79  * * sizeof() ensures that the expression is not evaluated at all, so
  80  *   its side-effects don't happen. That is to be consistent with the
  81  *   usual behaviour of debug-only constructs, such as assert().
  82  *
  83  * * `((_expr), 0)` uses the comma operator to swallow the actual type
  84  *   of `(_expr)`. This is to prevent VLAs from triggering evaluation.
  85  *
  86  * * `(void)` explicitly ignores the result of `(_expr)` and sizeof() so
  87  *   no "unused value" warning appears.
  88  */
  89
  90 #define BT_USE_EXPR(_expr)              ((void) sizeof((void) (_expr), 0))
  91 #define BT_USE_EXPR2(_expr1, _expr2)                                    \
  92         ((void) sizeof((void) (_expr1), (void) (_expr2), 0))
  93 #define BT_USE_EXPR3(_expr1, _expr2, _expr3)                            \
  94         ((void) sizeof((void) (_expr1), (void) (_expr2), (void) (_expr3), 0))
  95 #define BT_USE_EXPR4(_expr1, _expr2, _expr3, _expr4)                    \
  96         ((void) sizeof((void) (_expr1), (void) (_expr2),                \
  97                 (void) (_expr3), (void) (_expr4), 0))
  98 #define BT_USE_EXPR5(_expr1, _expr2, _expr3, _expr4, _expr5)            \
  99         ((void) sizeof((void) (_expr1), (void) (_expr2),                \
 100                 (void) (_expr3), (void) (_expr4), (void) (_expr5), 0))
 101
 102 #if defined __clang__
 103 #  if __has_warning("-Wunused-but-set-variable")
 104 #    define BT_DIAG_IGNORE_UNUSED_BUT_SET_VARIABLE \
 105         _Pragma("GCC diagnostic ignored \"-Wunused-but-set-variable\"")
 106 #  endif
 107 #endif
 108
 109 #if !defined BT_DIAG_IGNORE_UNUSED_BUT_SET_VARIABLE
 110 #  define BT_DIAG_IGNORE_UNUSED_BUT_SET_VARIABLE
 111 #endif
 112
 113 #ifdef __cplusplus
 114 }
 115 #endif
 116
 117 #endif