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=head1 TITLE
Allow exception-based error-reporting.
=head1 VERSION
Maintainer: Bennett Todd <[EMAIL PROTECTED]>
Date: 8 Aug 2000
Last Modified: 29 Aug 2000
Mailing List: [EMAIL PROTECTED]
Version: 3
Number: 70
Status: Developing
=head1 ABSTRACT
Allow full implementation of Fatal.pm, for programmers who prefer
exceptions for error reporting. To enable this, ensure that all
builtins (like e.g. print()) that return errors can be wrapped. In
addition, ensure that builtins like e.g. integer division, which
currently throw exceptions on errors, can have that behavior
switched off. At least glob, print, and printf should be wrappable.
=head1 DESCRIPTION
Perl has traditionally reflected the Unix syscall and library
tradition for error reporting: errors are indicated by
otherwise-impossible return values, which must be checked for
explicitly, lest system error events be ignored. Some programmers
prefer to have errors print a message and exit with non-zero status,
by default, rather than having to always code " || die ...". In
perl5 this has proven elusive of implementation.
Fatal.pm has been the attempt made to date, and it suffers from two
problems. One can be fixed with further development: it should have
various lists of builtins available, e.g. :io, :system, :all for
including all calls affecting I/O, all system calls of any sort, and
all calls that can have error returns. If these were a success, then
the requested category could also be posted into a testable
variable, allowing module authors who wished to to automatically
support this functionality as well.
In addition, for classes of errors that currently throw exceptions,
Fatal could be taught to disable them, allowing e.g.
no Fatal qw(:arithmetic);
my $result = 1 / 0; # $result now contains undef, w/
# error posted in $! or maybe $@
But Fatal.pm development stalls out early, because some builtins,
which report testable error conditions, cannot be wrapped. A
conspicuous example is print().
=head1 IMPLEMENTATION
Ensure that every perl builtin that can return an error, can be
wrapped. Perhaps in addition ensure that routines that currently die
on error, can have their behavior changed as well.
For the first part, tchrist posted a nice list of non-overridable
builtins; running my eye down it, it looks like the gross offenders
here are:
glob, print, printf
I don't know whether this is purely an implementation issue (and so
lies solely in the domain of perl6-internals) or whether any
programmer-visible changes may be necessary to allow this
(justifying posting to perl6-language).
=head1 REFERENCES
Fatal.pm, as included with recent perls.
Error.pm, available from CPAN, and cited by RFC 63: if this
proposal should carry, then Fatal.pm will see some very
active development, and if RFC 63 should also prevail, then
Fatal's development should be guided by RFC 63/Error.pm.
RFC 80 Proposes a taxonomy for exception objects; should it
prevail, it should guide the structure of exceptions thrown
when Fatal.pm gets worked on.
