[C++-sig] [Py++] user-defined exceptions

[Roman Yakovenko]

2009/3/25 Michał Nowotka <mmmnow at gmail.com>:
> And one more question - what about user-defined exceptions?
> Suppose I have following code from library which I cannot modify:
>
> namespace faif
>
> {
>
>
>   class FaifException : public std::exception {
>
>        public:
>
>                FaifException(){}
>
>                virtual ~FaifException() throw() {}
>
>                virtual const char *what() const throw() { return "FaifException"; }
>
>
>                virtual std::ostream& print(std::ostream& os) const throw();
>
>        };
>
>   class UserBreakException : public FaifException {
>
>    public:
>
>        UserBreakException(){}
>
>        virtual ~UserBreakException() throw() {}
>
>        virtual const char *what() const throw(){ return "UserBreak
> exception"; }
>
>
>        virtual std::ostream& print(std::ostream& os) const throw();
>
>    };
>
> (...)
>
> }
>
> This causes following warnings:
>
> WARNING: char const * faif::UserBreakException::what() const [member function]
>> warning W1046: The virtual function was declared with empty throw. Adding the ability to override the function from Python breaks the exception
>> specification. The function wrapper can throw any exception. In case of exception in run-time, the behaviour of the program is undefined!

I think this one is self-explained.

> WARNING: std::ostream & faif::UserBreakException::print(std::ostream &
> os) const [member function]
>> warning W1049: This method could not be overriden in Python - method returns reference to local variable!

The text should be different:
This method could not be overriden in Python - method returns *non
const* reference. In such cases, Boost.Python doesn't have place to
store the temporal variables.

> WARNING: std::ostream & faif::UserBreakException::print(std::ostream &
> os) const [member function]
>> warning W1046: The virtual function was declared with empty throw. Adding the ability to override the function from Python breaks the exception
>> specification. The function wrapper can throw any exception. In case of exception in run-time, the behaviour of the program is undefined!


> Should I exclude this declarations or there is another solution? (I am
> not sure excluding it may be called 'solution'...)

You may ignore them.

> BTW - Why warnings doesn't provide information form what header file
> particular warning was generated?

Because there was not demand to such functionality. A patch is welcome.

> BTW2 - How to exclude the whole class from generation?

c = mb.class_( <...> )
c.exclude()

I suggest you to take a look on the following document:
http://www.language-binding.net/pyplusplus/troubleshooting_guide/exceptions/exceptions.html

HTH

-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/