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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
47 lines
1.7 KiB
C++
47 lines
1.7 KiB
C++
#ifndef RUBY_BACKWARD2_STDARG_H /*-*-C++-*-vi:se ft=cpp:*/
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#define RUBY_BACKWARD2_STDARG_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 old #_
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*
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* Nobody should ever use these macros any longer. No konwn compilers lack
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* prototypes today. It's 21st century. Just forget them.
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*/
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#undef _
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#ifdef HAVE_PROTOTYPES
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# define _(args) args
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#else
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# define _(args) ()
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#endif
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#undef __
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#ifdef HAVE_STDARG_PROTOTYPES
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# define __(args) args
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#else
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# define __(args) ()
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#endif
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#ifdef __cplusplus
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#define ANYARGS ...
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#else
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#define ANYARGS
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#endif
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#endif /* RUBY_BACKWARD2_STDARG_H */
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