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

From: Beman Dawes (bdawes_at_[hidden])
Date: 2003-01-13 21:20:10

At 03:29 PM 1/13/2003, David Abrahams wrote:

 >Remember that it's a bad idea to carry dynamically-allocated state in
 >an exception object.

I wrestled with that a long time with the Filesystem Library, and finally 
ignored it. The advice is good in general, but there just didn't seem to be 
any way to meet the needs of users without carrying several paths (which 
contain std::strings.)

 >  Translating to readable strings at the throw
 >point is ill-advised.

Operating systems provide useful information (error descriptions translated 
into the local language, for example) which are easy to supply as readable 
strings as part of the exception, and hard for users to supply (because the 
user code would be non-portable). Thus the filesystem exceptions supply a 
nice, ready-to-use, what() message. For those users who want to roll their 
own, the detailed member functions supply detailed information. It seems to 
work well in practice, at least so far, and the exception mechanism is 
proportional in complexity to the rest of the library. All the alternatives 
I could think of (subsidiary classes and functions, adding levels of 
indirection) seemed way overcomplicated.

--Beman