On Mon, Aug 27, 2012 at 1:33 PM, Beman Dawes <bdawes@acm.org> wrote:
Ticket #7278 asks that Boost.System add C++11 noexcept support. A reasonable request, and I implemented it this morning by adding BOOST_NOEXCEPT at the appropriate places specified in the standard.
But there is a problem. noexcept is viral, so any classes that inherit from a class that uses noexcept must be changed to also use no except.
An example: Boost.Filesystem has this class:
class codecvt_error_cat : public boost::system::error_category { public: codecvt_error_cat(){} const char* name() const {return "codecvt";} std::string message(int ev) const; };
Compiling with GCC 4.7 -std=c++0x results in this error:
..\..\../boost/system/error_code.hpp:187:32: error: overriding 'virtual const char* boost::system::error_category::name() const noexcept (true)'
To fix it, the filesystem class has to be changed:
class codecvt_error_cat : public boost::system::error_category { public: codecvt_error_cat(){} const char* name() const BOOST_NOEXCEPT {return "codecvt";} std::string message(int ev) const; };
I've held off committing the Boost.System changes to trunk until we've had a chance to discuss how to approach this potential break to an unknown number of Boost and user libraries.
It looks like the affected Boost libraries are ASIO, Chrono, Filesystem, Thread, and of course System. I'll post a separate message describing a proposed [status] addition to the BOOST_NOEXCEPT* macros. --Beman --Beman