Macro overloading support in C.

cmacro_overload.h

/* MIT License
 *
 * Copyright (c) 2021 Tyge Løvset, NORCE, www.norceresearch.no
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#ifndef COVERLOAD_INCLUDED
#define COVERLOAD_INCLUDED

/*
Utility for overloading macros by different number of arguments.
Based on https://rextester.com/ONP80107
Example:

#define foo(...)       c_OVERLOAD(foo, __VA_ARGS__)
#define foo_0()        "Zero"
#define foo_1(x)       "One"
#define foo_2(x, y)    "Two"
#define foo_3(x, y, z) "Three"

#include <stdio.h>

int main()
{
    printf("%s %s %s %s\n", foo(), foo(1), foo(1, 2), foo(1, 2, 3));
}
*/

#define c_OVERLOAD(name, ...) _c_OVERLOAD_SELECT(name, _c_OVERLOAD_NUM_ARGS(__VA_ARGS__))(__VA_ARGS__)

#define _c_OVERLOAD_SELECT(name, num) _c_OVERLOAD_CONCAT(name, num)
#define _c_OVERLOAD_CONCAT(name, num) name ## _ ## num

#define _c_OVERLOAD_NUM_ARGS(...) _c_OVERLOAD_APPLY_ARG_N((_c_OVERLOAD_DETECT_0_ARGS(__VA_ARGS__), _c_OVERLOAD_RSEQ_N))
#define _c_OVERLOAD_APPLY_ARG_N(args) _c_OVERLOAD_ARG_N args
#define _c_OVERLOAD_DETECT_0_ARGS(...) _c_OVERLOAD_PREFIX_ ## __VA_ARGS__ ## SUFFIX
#define _c_OVERLOAD_PREFIX_SUFFIX ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,0

#define _c_OVERLOAD_ARG_N(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, \
                          _12, _13, _14, _15, _16, _17, _18, _19, _20, _21, \
                          _22, _23, _24, _25, _26, _27, _28, _29, _30, N, ...) N
#define _c_OVERLOAD_RSEQ_N \
    31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, \
    16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0

#endif