Nikita Nemkin, 29.08.2013 08:24: > On Thu, 29 Aug 2013 11:03:01 +0600, Stefan Behnel wrote: >> http://trac.cython.org/cython_trac/ticket/819 > > As your ticket mentions, there is a fundamental problem with method > inheritance. > (and with the way Cython generates forward declarations...) > > Any inherited method assumes 2 types simultaneously: the type of the base > method with 1st parameter being a base class pointer and the "actual" type > of the method with 1st parameter being derived class pointer. > 1st type, stored in method's Entry.type, is essentially the vtable slot > type. It's used when virtual method calls a made. It's also used for > generating > forward declarations and for casting in vtable init code. > 2nd type (stored in CFuncDef node) is used ONLY to generate function > definition. > > The mismatch between these 2 types is the root of the problem. > Before final methods were introduced, the 2nd ("actual") type was unimportant. > Method was cast to the vtable slot type in vtable init code and forgotten. > But final functions, bypassing vtable mechanic, rely soley on the 2nd type.
Thanks for writing up the analysis. > I have solved it for myself by storing BOTH types in the method entry > (Entry.type for the actual CFuncDef type and Entry.prev_type for the vtable > slot type). By using correct types in > generate_exttype_final_methods_declaration() > and generate_exttype_vtable_init_code() the problem is avoided. > You can see the patch here > https://github.com/nnemkin/cython/compare/final_subtypes Interesting. Your change dates back a while already. Were you planning to clean it up in some way before you submit it as pull request? > Notes for the patch: > * I removed a bit of wtf code from CFuncType.declaration_code, I'm not surprised. :) > * There is a disabled bug test named "inherited_final_method", And you had to disable it, because ... ? > you may want to remove/merge it with the test you modified. I already looked at it before I changed the main test. It appears to be a regression test for a specific bug that's different from the problem at hand, that's why I didn't touch it. Stefan _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
