On Tue, Aug 28, 2012 at 6:27 PM, Vicente J. Botet Escriba <vicente.botet@wanadoo.fr> wrote:
Le 28/08/12 23:22, Beman Dawes a écrit :
The three current BOOST_NOEXCEPT* macro variants miss the case where C++03 code has a "throw()" throw-specifier. Classes that derive from standard library exceptions need this to avoid breaking code on C++03 compilers.
I'm not enamored with the BOOST_NOEXCEPT_NOTHROW name, so feel free to offer suggestions for alternate names.
Here is the full set of macros:
#ifdef BOOST_NO_NOEXCEPT # define BOOST_NOEXCEPT # define BOOST_NOEXCEPT_NOTHROW throw() <---- new macro # define BOOST_NOEXCEPT_IF(Predicate) # define BOOST_NOEXCEPT_EXPR(Expression) false #else # define BOOST_NOEXCEPT noexcept # define BOOST_NOEXCEPT_NOTHROW noexcept <---- new macro # define BOOST_NOEXCEPT_IF(Predicate) noexcept((Predicate)) # define BOOST_NOEXCEPT_EXPR(Expression) noexcept((Expression)) #endif
Unless there are objections, I'll commit the changes Wednesday afternoon Eastern US time.
I have no major problem with the additional macro BOOST_NOEXCEPT_NOTHROW , but I don't see why it should be committed so quickly.
No real need, just wanting to clear it off my "half-done" list. (With Git, I could just stash my changes, but that's a bit of a pain with subversion.)
I will cal it BOOST_NOEXCEPT_OR_NOTHROW.
I considered that, but was put off by its length. BOOST_NOEXCEPT_OR_NOTHROW is clearer and the transition from throw() to noexcept is confusing, so let's got with BOOST_NOEXCEPT_OR_NOTHROW
My question is what macro will you use you implement noexcept in Boost.System. If you don't want to break c++03 compilers I think it should be BOOST_NOEXCEPT. Could you confirm?
Anything currently decorated with throw() has to use BOOST_NOEXCEPT_OR_NOTHROW. #include <stdexcept> class my_error : public std::runtime_error { public: const char* what() const throw() { return "bingo"; } }; For a C++03 compiler, replacing the throw() with BOOST_NOEXCEPT is equivalent to removing it. gcc 4.7 in C++03 mode will report an error: c:\mingw\4.7\bin\../lib/gcc/mingw32/4.7.0/include/c++/stdexcept:127:5: error: overriding 'virtual const char* std::runtime_error::what() const throw ()' Even for compilers that don't report this as an error, it is a silent change in semantics that can be avoided by using BOOST_NOEXCEPT_OR_NOTHROW. For example, class system_error has three signatures that need noexcept for C++11. All three of these are currently marked throw(), so all three have to be replaced with BOOST_NOEXCEPT_OR_NOTHROW. --Beman