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modules.h
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1/*
2 * Copyright (C) 2014 Freie Universität Berlin
3 * 2017 HAW-Hamburg
4 *
5 * This file is subject to the terms and conditions of the GNU Lesser
6 * General Public License v2.1. See the file LICENSE in the top level
7 * directory for more details.
8 */
9
21#ifndef MODULES_H
22#define MODULES_H
23
24#ifdef __cplusplus
25extern "C" {
26#endif
27
60#define IS_ACTIVE(macro) __is_active(macro)
61
71#define IS_USED(module) IS_ACTIVE(module)
72
76/* Here a prefix "__PREFIX_WHEN_" is added to the macro. So if it was a 1 we
77 * have "__PREFIX_WHEN_1", and if it was not defined we have "__PREFIX_WHEN_".
78 */
79#define __is_active(val) ___is_active(__PREFIX_WHEN_##val)
80
81/* With this placeholder we turn the original value into two arguments when the
82 * original value was defined as 1 (note the comma).
83 */
84#define __PREFIX_WHEN_1 0,
85
86/* Here we add two extra arguments, that way the next macro can accept varargs.
87 *
88 * If the original macro was defined as 1, this will have three arguments
89 * (__take_second_arg(0, 1, 0, 0)), otherwise it will have two
90 * (__take_second_arg(__PREFIX_WHEN_ 1, 0, 0)). The third zero is there just to
91 * be compliant with C99, which states that when a function-like macro ends
92 * with ellipsis (...) it should be called with at least one argument for the
93 * variable list.
94 */
95#define ___is_active(arg1_or_junk) __take_second_arg(arg1_or_junk 1, 0, 0)
96
97/* Finally, we just always take the second argument, which will be either 1
98 * (when three arguments are passed, i.e. macro was defined as 1) or 0 (when
99 * only two arguments are passed).
100 */
101#define __take_second_arg(__ignored, val, ...) val
106#ifdef __cplusplus
107}
108#endif
109
110#endif /* MODULES_H */