#ifndef RBIMPL_ATTR_NOEXCEPT_H /*-*-C++-*-vi:se ft=cpp:*/
#define RBIMPL_ATTR_NOEXCEPT_H
/**
* @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 `RBIMPL` or `rbimpl` 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 #RBIMPL_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 `noexcept` 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/internal/compiler_since.h"
#include "ruby/internal/has/feature.h"
/** Wraps (or simulates) C++11 `noexcept` */
#if ! defined(__cplusplus)
# /* Doesn't make sense. */
# define RBIMPL_ATTR_NOEXCEPT(_) /* void */
#elif RBIMPL_HAS_FEATURE(cxx_noexcept)
# define RBIMPL_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
#elif defined(__GXX_EXPERIMENTAL_CXX0X__) && __GXX_EXPERIMENTAL_CXX0X__
# define RBIMPL_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
#elif defined(__INTEL_CXX11_MODE__)
# define RBIMPL_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
#elif RBIMPL_COMPILER_SINCE(MSVC, 19, 0, 0)
# define RBIMPL_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
#elif __cplusplus >= 201103L
# define RBIMPL_ATTR_NOEXCEPT(_) noexcept(noexcept(_))
#else
# define RBIMPL_ATTR_NOEXCEPT(_) /* void */
#endif
#endif /* RBIMPL_ATTR_NOEXCEPT_H */
|