Re: [boost] [system] - system_error

From: Bo Persson (bop_at_[hidden])
Date: 2006-06-29 15:28:19

"Beman Dawes" <bdawes_at_[hidden]> skrev i meddelandet 
news:e80sim$5ng$1_at_sea.gmane.org...
>
> <Oliver.Kowalke_at_[hidden]> wrote in message 
> news:5D4F031442F5CB489CF88277DDBACCDD054D060B_at_drsse401.eu.infineon.com...
>> Hi,
>> shouldn't system_error::const char * what() const contain throw ()?
>
> Good question. I don't know the answer. The standard (for 
> std::exception, which is the eventual base class) says:
>
>    virtual const char* what() const throw();
>
> system_error::what catches exceptions, so it never throws.
>
> I afraid I still don't know the rule as to when you need to provide 
> a throw() specifier rather than just documenting that a function 
> never throws.
>
> Is there guidance from exception experts?

I'm not one of those, but have notice that several compilers (MSVC7.1, 
Comeau) complain about virtual functions having a less strict throw 
spec than the base class functions they override.

Seems to me like there would be a *real* surprise if

catch (const std::exception& e)
{
   e->what();
}

actually threw another exception, even if e is a derived exception 
class.

Bo Persson