86 lines
2.9 KiB
C++
86 lines
2.9 KiB
C++
/*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*
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* Copyright (C) 2019-2021 The DOSBox Staging Team
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef DOSBOX_COMPILER_H
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#define DOSBOX_COMPILER_H
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#include "config.h"
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// This header wraps compiler-specific features, so they won't need to
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// be hacked into the buildsystem.
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// Function-like macro __has_cpp_attribute was introduced in C++20, but
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// various compilers support it since C++11 as a language extension.
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// Thanks to that we can use it for testing support for both language-defined
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// and vendor-specific attributes.
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#ifndef __has_cpp_attribute // for compatibility with non-supporting compilers
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#define __has_cpp_attribute(x) 0
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#endif
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// Function-like macro __has_attribute was introduced in GCC 5.x and Clang,
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// alongside __has_cpp_attribute, and with the same logic.
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// See: https://clang.llvm.org/docs/LanguageExtensions.html#has-attribute
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#ifdef __has_attribute
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#define C_HAS_ATTRIBUTE 1
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#else
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#define C_HAS_ATTRIBUTE 0
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#define __has_attribute(x) 0 // for compatibility with non-supporting compilers
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#endif
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// The __attribute__ syntax is supported by GCC, Clang, and IBM compilers.
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//
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// Provided for backwards-compatibility with old code; to be gradually
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// replaced by new C++ attribute syntax.
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#if C_HAS_ATTRIBUTE
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#define GCC_ATTRIBUTE(x) __attribute__ ((x))
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#else
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#define GCC_ATTRIBUTE(x) /* attribute not supported */
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#endif
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// GCC_LIKELY macro is incorrectly named, because other compilers support
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// this feature as well (e.g. Clang, Intel); leave it be for now, at
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// least until full support for C++20 [[likely]] attribute will start arriving
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// in new compilers.
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//
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// Note: '!!' trick is used, to convert non-boolean values to 1 or 0
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// to prevent accidental incorrect usage (e.g. when user wraps macro
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// around a pointer or an integer, expecting usual C semantics).
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#if C_HAS_BUILTIN_EXPECT
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#define GCC_LIKELY(x) __builtin_expect(!!(x), 1)
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#define GCC_UNLIKELY(x) __builtin_expect(!!(x), 0)
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#else
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#define GCC_LIKELY
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#define GCC_UNLIKELY
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#endif
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// XSTR and STR macros can be used for turning defines into string literals:
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//
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// #define FOO 4
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// printf("It's a " STR(FOO)); // prints "It's a FOO"
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// printf("It's a " XSTR(FOO)); // prints "It's a 4"
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#define XSTR(s) STR(s)
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#define STR(s) #s
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#endif
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