Eric,
I think I've misled you.
You can have multiple bits of PERL_MAGIC_ext and a method of identifying
which bit you want is already there. Perl itself promises never to mess
with PERL_MAGIC_ext. The docs suggest it is meant to be private to the
extension using it. I think everything required is already in Perl.
The particular issue with wxPerl is that it uses the first member in
PERL_MAGIC_ext that it finds - perfectly reasonably as a module writer
might not expect an external extension to come along and mess with its
private data. This could be fixed within wxPerl - so that wxPerl does
get its own data despite Hash::Util::FieldHash.
Regards
Mark
On 02/12/2010 14:43, Eric J. Roode wrote:
Very interesting, Mark.
Long-term, I wonder if perhaps a change can be made to perl itself,
to manage conflicting uses of PERL_MAGIC_ext. So when an extension
calls the macro or function to store its data in the variable's magic,
perl tags it with something that identifies the extension, and files it
as part of the data. Then on fetching the data, perl looks up and
returns only that extension's data.
Medium-term, perhaps perl could be modified to croak gracefully
when someone stores data in PERL_MAGIC_ext when something's already
there. Ah, but then how could perl tell whether the extension is
updating its own data or overwriting someone else's data? You're left
with tagging again.
Short-term, I think you're right -- wxperl should put a marker on
its PERL_MAGIC_ext data, and croak gracefully when it reads data that it
didn't put there.
--
Eric J. Roode
On Wed, Dec 1, 2010 at 11:15 PM, Mark Dootson <[email protected]
<mailto:[email protected]>> wrote:
Hi,
The code actually dies at '$self->InsertColumn(0, 'Zero');'
wxPerl uses PERL_MAGIC_ext to store a pointer to the underlying
wxWidgets C object data. This bit of 'magic' is supposed to be for
the use of extensions. (like wxPerl).
Hash::Util::FieldHash also uses the PERL_MAGIC_ext belonging to the
wxPerl extensions to store some data.
When '$self->InsertColumn(0, 'Zero');', the 'magic' that wxPerl
retrieves no longer points to the wxObject - but to the
Hash::Util::FieldHash data - so bad things happen.
This particular issue could probably be fixed. It is possible to
have multiple bits of magic of the same type - and wxPerl could add
an identifier for its own magic and only retrieve the PERL_MAGIC_ext
that has that identifier.
However, reading the Hash::Util::FieldHash pod, that talks of
calling the DESTROY method of referenced objects, amongst other
things. I would expect there to be more work needed to accommodate
Hash::Util::FieldHash than just fixing the 'magic' issue.
Hope this is useful info.
