Custom GUCs still a bit broken

It seems like Custom GUCs are still in need of some work, as shown in my 
recent email. In particular, they are not transaction safe - if a 
transaction attempts to do DefineCustomFooVariable() and that 
transaction aborts, the placeholder setting that it used is already gone 
by the time it tries to roll back GUC settings. I think this code at the 
end of define_custom_variable()
       /*        * Free up as much as we conveniently can of the placeholder   structure        * (this neglects any
stackitems...)        */       set_string_field(pHolder, pHolder->variable, NULL);       set_string_field(pHolder,
&pHolder->reset_val,NULL);
 
       free(pHolder);


needs to be removed and instead we need to save pHolder in a list along 
with the GUC level, to be processed later by AtEOXact_GUC(), which would 
do the right thing according to whether or not it had a commit or an abort.

I want to get this fixed before we consider custom settings for plperl 
that have possible security implications.

Thoughts?

cheers

andrew