http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53398
--- Comment #2 from Roman Wieczorek <sweetrommie at gmail dot com> 2012-05-21 10:18:35 UTC --- (In reply to comment #1) > I think if we provide an option for this, we are > going to have people abuse this. The risk i see here is about compatibility of gcc compiled libraries with other object files. That's why i suggest changing vtable order only for a block of code, or for single class, like "__attribute__ ((__packed__)))" does. > Also I think the C++ ABIs between MS and GCC not compatible at all since they > use different mangling. Dynamic libraries (for windows) which follow COM spec, uses only pure virtual class. They do not export class them in the dll, but provides an ansi C function for creating an object. In such cases the only exported objects are C functions. It also avoids C++ name mangling problems. As it goes for dll i met, it works. Probably because COM was well documented. The only problem I found, is the order of overloaded functions. COM does not allow overloading. Here the method i showed helps and library becomes compatible. > MS does not follow the cross target/compiler ABI (IA64 > C++ ABI). The docs shows it is in section 2.5.3.1 http://sourcery.mentor.com/public/cxx-abi/abi.html#vtable It is similar in COM spec (chapter 3) http://www.daimi.au.dk/~datpete/COT/COM_SPEC/pdf/com_spec.pdf No idea why msc behaves overloaded functions different.
