Defer in C for GCC and CLANG

defer.h

/*
 * MIT License
 * 
 * Copyright (c) 2025 Arvid Gerstmann
 * 
 * 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 RL_DEFER_H__
#define RL_DEFER_H__

#ifdef __clang__

    static inline __attribute__((always_inline)) void
    _defer_cleanup(void (^*b)(void)) { (*b)(); }

    #define __DEFER__(F, V)       \
        __attribute__((cleanup(_defer_cleanup))) void (^V)(void) = ^
    #define __DEFER_(N) __DEFER__(__DEFER_FUNCTION_ ## N, __DEFER_VARIABLE_ ## N)
    #define __DEFER(N) __DEFER_(N)
    #define defer __DEFER(__COUNTER__)

#else /* gcc */

    #define __DEFER__(F, V)      \
        auto inline __attribute__((always_inline)) void F(int*);         \
        __attribute__((cleanup(F))) int V; \
        inline __attribute__((always_inline)) void F(int*)
    #define __DEFER_(N) __DEFER__(__DEFER_FUNCTION_ ## N, __DEFER_VARIABLE_ ## N)
    #define __DEFER(N) __DEFER_(N)
    #define defer __DEFER(__COUNTER__)

#endif

#endif /* RL_DEFER_H__ */