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According to MSVC manual (*1), cl.exe can skip including a header file when that: - contains #pragma once, or - starts with #ifndef, or - starts with #if ! defined. GCC has a similar trick (*2), but it acts more stricter (e. g. there must be _no tokens_ outside of #ifndef...#endif). Sun C lacked #pragma once for a looong time. Oracle Developer Studio 12.5 finally implemented it, but we cannot assume such recent version. This changeset modifies header files so that each of them include strictly one #ifndef...#endif. I believe this is the most portable way to trigger compiler optimizations. [Bug #16770] *1: https://docs.microsoft.com/en-us/cpp/preprocessor/once *2: https://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.html
72 lines
3.2 KiB
C++
72 lines
3.2 KiB
C++
#ifndef RUBY3_TOKEN_PASTE_H /*-*-C++-*-vi:se ft=cpp:*/
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#define RUBY3_TOKEN_PASTE_H
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/**
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* @file
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* @author Ruby developers <ruby-core@ruby-lang.org>
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* @copyright This file is a part of the programming language Ruby.
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* Permission is hereby granted, to either redistribute and/or
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* modify this file, provided that the conditions mentioned in the
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* file COPYING are met. Consult the file for details.
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* @warning Symbols prefixed with either `RUBY3` or `ruby3` are
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* implementation details. Don't take them as canon. They could
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* rapidly appear then vanish. The name (path) of this header file
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* is also an implementation detail. Do not expect it to persist
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* at the place it is now. Developers are free to move it anywhere
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* anytime at will.
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* @note To ruby-core: remember that this header can be possibly
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* recursively included from extension libraries written in C++.
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* Do not expect for instance `__VA_ARGS__` is always available.
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* We assume C99 for ruby itself but we don't assume languages of
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* extension libraries. They could be written in C++98.
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* @brief Defines #RUBY3_TOKEN_PASTE.
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*/
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#include "ruby/3/config.h"
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/* :TODO: add your compiler here. There are many compilers that can suppress
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* warnings via pragmas, but not all of them accept such things inside of `#if`
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* and variants' conditions. And such nitpicking behavours tend not be
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* documented. Please improve this file when you are really sure about your
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* compiler's behaviour. */
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#if RUBY3_COMPILER_SINCE(GCC, 4, 2, 0)
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# /* GCC is one of such compiler who cannot write `_Pragma` inside of a `#if`.
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# * Cannot but globally kill everything. This is of course a very bad thing.
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# * If you know how to reroute this please tell us. */
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# /* https://gcc.godbolt.org/z/K2xr7X */
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# define RUBY3_TOKEN_PASTE(x, y) TOKEN_PASTE(x, y)
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# pragma GCC diagnostic ignored "-Wundef"
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# /* > warning: "symbol" is not defined, evaluates to 0 [-Wundef] */
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#elif RUBY3_COMPILER_IS(Intel)
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# /* Ditto for icc. */
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# /* https://gcc.godbolt.org/z/pTwDxE */
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# define RUBY3_TOKEN_PASTE(x, y) TOKEN_PASTE(x, y)
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# pragma warning(disable: 193)
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# /* > warning #193: zero used for undefined preprocessing identifier */
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#elif RUBY3_COMPILER_BEFORE(MSVC, 19, 14, 26428)
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# /* :FIXME: is 19.14 the exact version they supported this? */
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# define RUBY3_TOKEN_PASTE(x, y) TOKEN_PASTE(x, y)
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# pragma warning(disable: 4668)
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# /* > warning C4668: 'symbol' is not defined as a preprocessor macro */
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#elif RUBY3_COMPILER_IS(MSVC)
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# define RUBY3_TOKEN_PASTE(x, y) \
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RUBY3_WARNING_PUSH() \
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RUBY3_WARNING_IGNORED(4668) \
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TOKEN_PASTE(x, y) \
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RUBY3_WARNING_POP()
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#elif RUBY3_HAS_WARNING("-Wundef")
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# define RUBY3_TOKEN_PASTE(x, y) \
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RUBY3_WARNING_PUSH() \
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RUBY3_WARNING_IGNORED(-Wundef) \
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TOKEN_PASTE(x, y) \
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RUBY3_WARNING_POP()
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#else
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# /* No way. */
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# define RUBY3_TOKEN_PASTE(x, y) TOKEN_PASTE(x, y)
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#endif
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#endif /* RUBY3_TOKEN_PASTE_H */
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