Re: [boost] Re: Formal Review: The Spirit Parser Framework.

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-10-12 08:01:13

At 03:05 AM 10/12/2002, Ross Smith wrote:
 >On Saturday, 12 October 2002 18:28, Joel de Guzman wrote:
 >>
 >> From: "Carl Daniel" <cpdaniel_at_[hidden]>
 >>
 >> > Exception classes thrown by Spirit (parser_error<>,
 >> > illegal_backtracking) don't derive from std::exception - shouldn't
 >> > they?
 >>
 >> I'm not sure. Should it? What will be the benefits in doing so?
 >> The truth is, I'm not quite happy with the standard C++ exceptions.
 >> For one, it's hard coded the what() to be a string.
 >
 >The big advantage of requiring all exceptions to be derived from
 >std::exception, as I see it, is that you can write your main function
 >like this...
 >
 >    int main() {
 >      try {
 >        // code goes here
 >        return 0;
 >      }
 >      catch (const std::exception& ex) {
 >        std::cerr << "*** " << ex.what() << "\n";
 >        return EXIT_FAILURE;
 >      }
 >    }
 >
 >...and be confident of getting an error message instead of a crash if
 >anything gets thrown that you haven't explicitly caught.

Yes, and that idiom is so useful that Boost.Test provides library code to 
handle the details.

 > You can do the
 >same thing in other functions that you don't want anything to escape
 >from (e.g. destructors, extern "C" functions that will be used as
 >callbacks, etc). If you can't rely on everything having std::exception
 >in its family tree, you have to either use catch (...), which denies
 >you the chance of logging any meaningful error message, or write a
 >whole stack of catch clauses for every exception you can think of.
 >
 >I'd like to suggest (to the Boost readership in general) that this
 >should be made a requirement for all Boost libraries.

I agree, unless there is some application specific reason why another 
approach is better.

--Beman