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c37a357c13
This reverts commit443389effc. This reverts commitd94960f22e. Inclusion of header files must be explicit. Every file shall directly include what is necessary. https://github.com/include-what-you-use/include-what-you-use says: > When every file includes what it uses, then it is possible to edit any > file and remove unused headers, without fear of accidentally breaking > the upwards dependencies of that file. It also becomes easy to > automatically track and update dependencies in the source code. Though we don't use iwyu itself, the principle quoted above is a good thing that we can agree. Now that include guards were added to every and all of the headers inside of our project this changeset does not increase compile time, at least on my machine.
91 lines
4.1 KiB
C++
91 lines
4.1 KiB
C++
#ifndef RUBY3_ATTR_NOEXCEPT_H /*-*-C++-*-vi:se ft=cpp:*/
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#define RUBY3_ATTR_NOEXCEPT_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_ATTR_NOEXCEPT.
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*
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* This isn't actually an attribute in C++ but who cares...
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*
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* Mainly due to aesthetic reasons, this one is rarely used in the project.
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* But can be handy on occasions, especially when a function's noexcept-ness
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* depends on its calling functions.
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*
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* ### Q&A ###
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*
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* - Q: Can a function that raises Ruby exceptions be attributed `noexcept`?
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*
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* - A: Yes. `noexcept` is about C++ exceptions, not Ruby's. They don't
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* interface each other. You can safely attribute a function that raises
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* Ruby exceptions as `noexcept`.
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*
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* - Q: How, then, can I assert that a function I wrote doesn't raise any Ruby
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* exceptions?
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*
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* - A: `__attribute__((__leaf__))` is for that purpose. A function attributed
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* as leaf can still throw C++ exceptions, but not Ruby's. Note however,
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* that it's extremely difficult -- if not impossible -- to assert that a
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* function doesn't raise any Ruby exceptions at all. Use of that
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* attribute is not recommended; mere mortals can't properly use that by
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* hand.
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*
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* - Q: Does it make sense to attribute an inline function `noexcept`?
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*
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* - A: I thought so before. But no, I don't think they are useful any longer.
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*
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* - When an inline function attributed `noexcept` actually doesn't throw
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* any exceptions at all: these days I don't see any difference in
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* generated assembly by adding/removing this attribute. C++ compilers
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* get smarter and smarter. Today they can infer if it actually throws
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* or not without any annotations by humans (correct me if I'm wrong).
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*
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* - When an inline function attributed `noexcepr` actually _does_ throw an
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* exception: they have to call `std::terminate` then (C++ standard
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* mandates so). This means exception handling routines are actually
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* enforced, not omitted. This doesn't impact runtime performance (The
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* Itanium C++ ABI has zero-cost exception handling), but does impact on
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* generated binary size. This is bad.
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*/
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#include "ruby/3/compiler_since.h"
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#include "ruby/3/has/feature.h"
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/** Wraps (or simulates) C++11 `noexcept` */
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#if ! defined(__cplusplus)
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# /* Doesn't make sense. */
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# define RUBY3_ATTR_NOEXCEPT(_) /* void */
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#elif RUBY3_HAS_FEATURE(cxx_noexcept)
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# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
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#elif defined(__GXX_EXPERIMENTAL_CXX0X__) && __GXX_EXPERIMENTAL_CXX0X__
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# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
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#elif defined(__INTEL_CXX11_MODE__)
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# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
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#elif RUBY3_COMPILER_SINCE(MSVC, 19, 0, 0)
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# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
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#elif __cplusplus >= 201103L
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# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
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#else
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# define RUBY3_ATTR_NOEXCEPT(_) /* void */
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#endif
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#endif /* RUBY3_ATTR_NOEXCEPT_H */
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