add/remove fitlers internals issues

[Stas Bekman <st...@stason.org>]

Currently filters are registered via 4 names and then the same name is re-used 
to push one to many mod_perl filters. The problem with this implementation is 
that we can't remove filters. And I think we should be able to remove filters 
that were added dynamically. This requires a re-design of the filters 
registration/addition mechanism, where instead of the four names we use the 
real name of the filter should be used when registering/adding it.

This is doable with filters registered by using their sub name or name 
resolved from a coderef, as long as it's not an anonymous coderef. How can we 
handle this for anonymous coderefs? If I understand correctly, there are two 
problems with anonymous coderefs:

1. two different interpreters may give two different functions the same CODE 
reference address, so we can's just use the CODE address as a function name.
2. the original interpreter must be stored and used when running it, but what 
happens to the interpreter that was selected to run that particular phase? The 
original interpreter might be from a different pool, and it's a big pandora box.

I guess these are the same reasons why we still have not implemented the 
resolving of anonymous coderefs in modperl_mgv_name_from_sv. So how can we 
approach this issue?

Another issue is with add filter functions (e.g., $r->add_input_filter()). The 
file todo/filters.txt (which seems to be quite outdated) suggest to pass an 
optional $ctx:

   $r->add_output_filter($name, $ctx)

Though I think it's problematic. What happens if $ctx is created by one 
interpreter, but then the filter run by another one? I know that we can store 
the pointer to the original interpreter that has created $ctx, but once we run 
the filter we will have to set that interpreter as the current, ignoring the 
interpreter that was selected to run the filter handler. Do you see the 
problem here? It's the same issue as #2 I've listed above.

__________________________________________________________________
Stas Bekman            JAm_pH ------> Just Another mod_perl Hacker
http://stason.org/     mod_perl Guide ---> http://perl.apache.org
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