develooper Front page | perl.perl5.porters | Postings from November 2003

Re: DynaLoader (was Re: [5.12.0] Proposal for changing UNIVERSAL semantics)

Thread Previous | Thread Next
Michael G Schwern
November 6, 2003 21:09
Re: DynaLoader (was Re: [5.12.0] Proposal for changing UNIVERSAL semantics)
Message ID:
On Thu, Nov 06, 2003 at 07:32:45PM +0000, Graham Barr wrote:
> On Nov 6, 2003, at 2:00, Michael G Schwern wrote:
> >On Wed, Nov 05, 2003 at 09:05:52PM +0000, Graham Barr wrote:
> >>On Nov 4, 2003, at 23:13, Michael G Schwern wrote:
> >>>So, basically, you pick up an AUTOLOAD by inheriting from any module
> >>>that
> >>>uses XS.  Feeling paranoid yet? :)  Should we change can() to ignore
> >>>methods inherited from DynaLoader now?
> >>
> >>Thats been a known issue for a long time. The only reason you need to
> >>inherit from DynaLoader is that bootstrap may call the dl_load_flags
> >>method.
> >
> >Are you sure you mean dl_load_flags?  It appears that the autoloaded
> >methods are:
> What has autoloaded subs got todo with inheritance ?

Sorry, I misparsed the above as "the only reason DynaLoader needs to inherit 
from AutoLoader".  AutoLoader on the brane.

> >>The annoying thing is that because you do have AUTOLOAD there then you
> >>get different warnings.
> >
> >I've been pondering changing the AutoLoader error message so it looks
> >a bit more like a normal method/function lookup failure.  Possibly
> >placing the normal error in front of the extended AutoLoader 
> >information.
> >This way at least checks like
> >$@ =~ /^Can't locate object method "$meth" via package "$class"/ will
> >still work.
> But AutoLoader::AUTOLOAD has no way to be sure if what is being 
> attempted to be loaded was called as a method or a sub

Yeah, there's the rub.  I wonder if it could take an educated guess somehow.
Check if the first argument is an object.  Of course, then class methods
won't work.  *ponder*.

Pragmaticly, I've rarely seen anyone check for.
	$@ =~ /^Undefined subroutine &${pack}::$func called/

Having AutoLoader spit out the normal method lookup failure message,
regardless of whether it was a function or method call, is at least less 
wrong than its current behavior.  Doesn't really make me happy though.

Or we could do a fix for DynaLoader::AUTOLOAD similar to UNIVERSAL::import.
Limit its scope.  Since the autoloaded things in DynaLoader are functions...

    sub AUTOLOAD {
	my($class, $meth) = $DynaLoader::AUTOLOAD =~ /^(.*)::([^:]+)$/;
	croak qq{Can't locate object method "$meth" via package "$class"} 
            unless $class eq 'DynaLoader';

	$AutoLoader::AUTOLOAD = $DynaLoader::AUTOLOAD;
	goto &AutoLoader::AUTOLOAD;

This still leaves us with the wrong message should someone say:

    package Foo;
    require DynaLoader;
    @ISA = qw(DynaLoader);


but its less wrong than "Can't locate auto/Foo/".  With "Use of 
inherited AUTOLOAD for non-method Foo::bar() is deprecated" warning 
that goes along with it I think its less confusing.

Michael G Schwern
11. Every old idea will be proposed again with a different name and
    a different presentation, regardless of whether it works.
     -- RFC 1925

Thread Previous | Thread Next Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at | Group listing | About