🚀 go-pugleaf

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]
>
>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."
>
>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."

Section 19.1/1 (that is, section 19.1 paragraph 1) of the Jan 96 draft
states it more clearly:

|   19.1  Exception classes                           [lib.std.exceptions]
| 
| 1 The Standard C++ library provides classes to be used to report certain
|   errors (_lib.res.on.exception.handling_)  in  C++  programs.

Note that section 19.1.1 is

|  19.1.1  Class logic_error                            [lib.logic.error]

which is probably not the section to which you were referring.  I find
it helpful to use `.' for sub-section numbers and `/' for paragraph
numbers, to avoid confusion.

>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?

I believe the emphasis on "by *C++ Standard library components*" was
simply intended to stress the point that other C++ code didn't have
to throw only objects derived from class `exception' (as I believe was
mooted in some previous designs for C++ exception handling).
It was not intended to suggest that user's C++ code could not do so,
only that they did not have to do so.  I guess this wording was
recognized as being confusing, since it has now been replaced.

I would still consider Plauger's advice quoted above as good advice.

--
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WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh@128.250.37.3         |     -- the last words of T. S. Garp.
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