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author | 卜部昌平 <shyouhei@ruby-lang.org> | 2020-04-08 13:28:13 +0900 |
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committer | GitHub <noreply@github.com> | 2020-04-08 13:28:13 +0900 |
commit | 9e6e39c3512f7a962c44dc3729c98a0f8be90341 (patch) | |
tree | 901a22676d54d78240e450b64a8cd06eb1703910 /include/ruby/3/attr/noexcept.h | |
parent | 5ac4bf2cd87e1eb5779ca5ae7f96a1a22e8436d9 (diff) | |
download | ruby-9e6e39c3512f7a962c44dc3729c98a0f8be90341.tar.gz |
Merge pull request #2991 from shyouhei/ruby.h
Split ruby.h
Diffstat (limited to 'include/ruby/3/attr/noexcept.h')
-rw-r--r-- | include/ruby/3/attr/noexcept.h | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/include/ruby/3/attr/noexcept.h b/include/ruby/3/attr/noexcept.h new file mode 100644 index 0000000000..c5db6b3e79 --- /dev/null +++ b/include/ruby/3/attr/noexcept.h @@ -0,0 +1,90 @@ +/** \noop-*-C++-*-vi:ft=cpp + * @file + * @author Ruby developers <ruby-core@ruby-lang.org> + * @copyright This file is a part of the programming language Ruby. + * Permission is hereby granted, to either redistribute and/or + * modify this file, provided that the conditions mentioned in the + * file COPYING are met. Consult the file for details. + * @warning Symbols prefixed with either `RUBY3` or `ruby3` are + * implementation details. Don't take them as canon. They could + * rapidly appear then vanish. The name (path) of this header file + * is also an implementation detail. Do not expect it to persist + * at the place it is now. Developers are free to move it anywhere + * anytime at will. + * @note To ruby-core: remember that this header can be possibly + * recursively included from extension libraries written in C++. + * Do not expect for instance `__VA_ARGS__` is always available. + * We assume C99 for ruby itself but we don't assume languages of + * extension libraries. They could be written in C++98. + * @brief Defines #RUBY3_ATTR_NOEXCEPT. + * + * This isn't actually an attribute in C++ but who cares... + * + * Mainly due to aesthetic reasons, this one is rarely used in the project. + * But can be handy on occasions, especially when a function's noexcept-ness + * depends on its calling functions. + * + * ### Q&A ### + * + * - Q: Can a function that raises Ruby exceptions be attributed `noexcept`? + * + * - A: Yes. `noexcept` is about C++ exceptions, not Ruby's. They don't + * interface each other. You can safely attribute a function that raises + * Ruby exceptions as `noexcept`. + * + * - Q: How, then, can I assert that a function I wrote doesn't raise any Ruby + * exceptions? + * + * - A: `__attribute__((__leaf__))` is for that purpose. A function attributed + * as leaf can still throw C++ exceptions, but not Ruby's. Note however, + * that it's extremely difficult -- if not impossible -- to assert that a + * function doesn't raise any Ruby exceptions at all. Use of that + * attribute is not recommended; mere mortals can't properly use that by + * hand. + * + * - Q: Does it make sense to attribute an inline function `noexcept`? + * + * - A: I thought so before. But no, I don't think they are useful any longer. + * + * - When an inline function attributed `noexcept` actually doesn't throw + * any exceptions at all: these days I don't see any difference in + * generated assembly by adding/removing this attribute. C++ compilers + * get smarter and smarter. Today they can infer if it actually throws + * or not without any annotations by humans (correct me if I'm wrong). + * + * - When an inline function attributed `noexcepr` actually _does_ throw an + * exception: they have to call `std::terminate` then (C++ standard + * mandates so). This means exception handling routines are actually + * enforced, not omitted. This doesn't impact runtime performance (The + * Itanium C++ ABI has zero-cost exception handling), but does impact on + * generated binary size. This is bad. + */ +#include "ruby/3/compiler_since.h" +#include "ruby/3/has/feature.h" + +/** Wraps (or simulates) C++11 `noexcept` */ +#if defined(RUBY3_ATTR_NOEXCEPT) +# /* Take that. */ + +#elif ! defined(__cplusplus) +# /* Doesn't make sense. */ +# define RUBY3_ATTR_NOEXCEPT(_) /* void */ + +#elif RUBY3_HAS_FEATURE(cxx_noexcept) +# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_)) + +#elif defined(__GXX_EXPERIMENTAL_CXX0X__) && __GXX_EXPERIMENTAL_CXX0X__ +# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_)) + +#elif defined(__INTEL_CXX11_MODE__) +# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_)) + +#elif RUBY3_COMPILER_SINCE(MSVC, 19, 0, 0) +# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_)) + +#elif __cplusplus >= 201103L +# define RUBY3_ATTR_NOEXCEPT(_) noexcept(noexcept(_)) + +#else +# define RUBY3_ATTR_NOEXCEPT(_) /* void */ +#endif |