Oleg Abrosimov wrote:
Hello Jeremy!
There is a strong opinion against catch(...) clause. But problems, mentioned by Alexander Nasonov and Ames Andreas could be worked around.
1) define a BOOST_BROKEN_CATCH_ALL configuration macro that is non-zero when compiling in mode where catch(...) is dangerous (BOOST_MSVC is defined and _MSC_VER is in a predefined range. according to Peter Dimov MSVC 8 doesn't catch SEH exceptions with ... by default) 2) protect all code in your catcher.hpp with this macro and place #error message in #else branch that describes the problem with catch(...) on a given platform. Later it can be replaced with macroses, proposed by Alexander Nasonov: try { throw std::logic_error("testing"); } BOOST_CATCH_PP_SEQ((ex1)(ex2)(ex3), my_exception_handler());
Does proposed workaround have uniform behavior on all platforms?
alternatively or additionally, you can provide here an implementation that catches not for ... but for std::exception& It completely eliminates the original problem but restricts user to only std::exception - derived exceptions.
to extend this approach a bit you can provide user a possibility to define BOOST_EXCEPTION_BASE_1, BOOST_EXCEPTION_BASE_2, etc up to predefined limit. and use these macros to catch (BOOST_EXCEPTION_BASE_N) for all N defined by user.
Alexander? Ames? What do you prefer here?
When I jumped in into this discussion, I didn't intend to produce new boost library as I didn't like use of rethrow. I believe that exception handling should be very simple and not require a lot of metaprogramming like sorting handlers, creating MPL sequence of handled exception on the fly and so on. So, this library should a simple utility library that doesn't rethow if possible and doesn't hide a lot from a user. 1. Catch a list of exceptions in one line: try { throw std::logic_error("testing"); } BOOST_CATCH_PP_SEQ((ex1)(ex2)(ex3), my_exception_handler()); There is no need for MPL counterpart because you can always transform PP sequence into MPL sequence (but this functionaly seems to be missing in boost). If you can't do that (e.g. you need to mpl::push_back, or apply mpl::transform_view), then this library goes beyond a simple utility ;-) 2. Catch and dispatch (or visit, if you like) try { throw std::logic_error("testing"); } BOOST_CATCH_AND_DISPATCH(std::exception&, my_exception_handler()); This code rethows but it doesn't catch(...) but rather catch(std::exception&). Needless to say that my_exception_handler should be as simple as possible. Macros inside this class should be avoided because it's often impossible to go to a definition of a function inside it. Currently, my_exception_handler in item 1 has different (and much simpler) interface compared to that from item 2. It would be nice to have common interface. -- Alexander Nasonov Project Manager at Akmosoft ( http://www.akmosoft.com ) Blog: http://nasonov.blogspot.com Email: $(FirstName) dot $(LastName) at gmail dot com