Re: Re: [boost] Re: Next revision of boost::thread & OS error code.

From: Beman Dawes (bdawes_at_[hidden])
Date: 2003-01-12 20:39:40

At 05:15 PM 1/10/2003, William E. Kempf wrote:

 >>        ... what() // from std::runtime_error. Implementation provides
 >>                   // a very explicit message, including who(), path1(),
 >>                   // path2(), and message reported by O/S (which is
 >>                   // subject to locale on some O/S's.
 >>
 >>        int native_error() const;
 >>        // a return of 0 implies a library (rather than system) error
 >>
 >>        error_code error() const;  // filesystem defined error code
 >>
 >>        const std::string &  who() const; // name of func throwing
 >exception
 >>
 >>        const path & path1() const; // argument 1 to func; may be 
empty()
 >>        const path & path2() const; // argument 2 to func; may be 
empty()
 >>
 >> That's pretty heavyweight, but each function has important uses.
 >
 >This description brings a better understanding than what I had 
previously,
 >but doesn't fill in all the gaps.
 >
 >What's the purpose of a non-native error code?

It is useful for those who want a portable, more detailed breakdown of what 
caused the error. The alternative was no non-native error code, but instead 
providing one exception class for each of what are now error codes.

 >  For that matter, if what()
 >includes a translated message for the error code, what purpose is there 
for
 >the native error code?

People said they wanted it, and the cost is low (one int). I think Greg is 
right that they wanted to attempt system-dependent recovery.

Note that there is no requirement on what(). As a QOI I tried to deliver a 
very informative message, but don't want to try to mandate that. Also, 
whether the localized message actually is in the right language for the 
user depends on a lot more than what the O/S thinks is the right locale.

 >The thread will always be the current thread, so there's no need to carry 

 >that payload.

Duh!

--Beman