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In article <9604121530.AA08606@sun132.spd.dsccc.com>
kcline@spdmail.spd.dsccc.com (Kevin Cline) writes:

>In "The Standard C++ Library" on page 65, Plauger wrote:
>
>  "I strongly encourage you to follow the lead of the Standard C++
>   library in the use of exceptions:
>   * Throw only objects of one or more classes derived from [exception]
>

Good advice.

>Page 19-1 of the 4/95 version of the draft says "The Standard C++
>library provides classes to be used to report errors in C++ programs."
>

True.

>But in section 19.1.1 of the same draft it says:
>
>"The class exception defines the base class for the  types  of  objects
> thrown  as  exceptions by *C++ Standard library components*, and certain
> expressions, to report errors detected during program execution."
>

Also true.

>Can someone on the committee indicate whether it was the committee's
>intention for the standard exception class hierarchy to be used in
>general C++ programming, or whether the intention was for the standard
>exception class hierarchy to be reserved to the Standard C++ library?
>

The intention was for the exception class hierarchy to serve well as
a basis for your own exception classes and as all the concrete exception
classes the library itself needs.  You can derive from exception, which is
almost an abstract class, or you can derive from its derivatives.

>Another developer on our team has asked
>  How can we be sure that ANSI C++ library callbacks work
>  correctly in the face of exceptions?  What if ANSI C++
>  library code catches *our* exception?
>

Not to worry.

>Is this a problem, or are library functions required to reraise any
>exceptions thrown by client code? 
>

Client exceptions are intended to be pass through library code uncaught, or
at least reraised.

Greg Colvin
gregor@netcom.com
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