src/common/macros.h

   1 #ifndef _BABELTRACE_INTERNAL_H
   2 #define _BABELTRACE_INTERNAL_H
   3
   4 /*
   5  * Copyright 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23  * SOFTWARE.
  24  */
  25
  26
  27 #define bt_max_t(type, a, b)    \
  28         ((type) (a) > (type) (b) ? (type) (a) : (type) (b))
  29
  30 /*
  31  * BT_HIDDEN: set the hidden attribute for internal functions
  32  * On Windows, symbols are local unless explicitly exported,
  33  * see https://gcc.gnu.org/wiki/Visibility
  34  */
  35 #if defined(_WIN32) || defined(__CYGWIN__)
  36 #define BT_HIDDEN
  37 #else
  38 #define BT_HIDDEN __attribute__((visibility("hidden")))
  39 #endif
  40
  41 /*
  42  * Yield `ref`'s value while setting `ref` to NULL.
  43  *
  44  * This can be used to give a strong reference to a callee:
  45  *
  46  *   add_foo_to_list(list, BT_MOVE_REF(foo));
  47  *
  48  * or in a simple assignment:
  49  *
  50  *   my_struct->foo = BT_MOVE_REF(foo);
  51  *
  52  * When moving a reference in a function call, the reference is given to the
  53  * callee even if that function call fails, so make sure the called function
  54  * is written accordingly.
  55  */
  56
  57 #define BT_MOVE_REF(ref)                \
  58         ({                              \
  59                 __auto_type _ref = ref; \
  60                 ref = NULL;             \
  61                 _ref;                   \
  62         })
  63
  64 #endif