🔖 prelude
Useful C header files
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hint.h
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1/*
2 * 🔖 prelude - debug.h
3 * Copyright (c) 2026 Fawn <rubiefawn@gmail.com>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
20#pragma once
21
34#if defined(__cplusplus) && __cpp_lib_unreachable >= 202202L
35 #include <utility>
36 #define unreachable() std::unreachable()
37#elif __STDC_VERSION__ < 202311L || !defined(unreachable)
38 #ifdef _MSC_VER
39 #define unreachable() __assume(0)
40 #elif defined(__GNUC__) || defined(__clang__)
41 #define unreachable() __builtin_unreachable()
42 #elif __STDC_VERSION__ >= 201112L
43 _Noreturn static inline void __c11_unreachable(void) {}
44 #define unreachable() __c11_unreachable()
45 #else
46 #warning No suitable compiler intrinsic found, unreachable() will have no effect
47 #define unreachable()
48 #endif
49#endif
50
68#ifndef NDEBUG
69 #define assume(COND)
70#elif __cplusplus >= 202302L
71 #define assume(COND) [[assume(COND)]]
72#elif defined(_MSC_VER)
73 #define assume(COND) __assume(COND)
74#elif defined(__clang__)
75 #define assume(COND) __builtin_assume(COND)
76#elif defined(__GNUC__)
77 #if __has_attribute(assume)
78 #define assume(COND) [[gnu::assume(COND)]]
79 #endif
80#endif
81#ifndef assume
82 #ifdef unreachable
83 #warning assume() will evaluate its condition parameter, avoid using conditions with side effects
84 #define assume(COND) do { if (COND) {} else { unreachable(); } } while (0)
85 #else
86 #warning No suitable compiler intrinsic found, assume() will have no effect
87 #define assume(COND)
88 #endif
89#endif