me and arai chat on using xpcom from jsctypes

chat.md

02:13:32: <noida> hey arai do you think its possible (im thinking it should be) to get into xpcom from ctypes with vtables?
02:13:54: <noida> or does it have to be exposed with extern c first or something?
02:14:35: <Arai> Possible, I guess
02:15:02: <Arai> What you need is figuring out the converted function name
02:15:04: <noida> even without an extern c?
02:16:06: <Arai> Do you know that the function symbol name in C++ is different from C?
02:17:07: <noida> would it be ok if i eventually write up how to use xpcom on mdn? :D
02:17:52: <Arai> a bit scary
02:18:03: <noida> ah ok as it might lead to exploits?
02:18:44: <Arai> actually I'm not sure what would happen with it
02:22:45: <Arai> so, if you've compile it as C, you'll see "0000000100000f70 T _someFunction" in nm output
02:22:57: <Arai> the address will be different tho
02:23:03: <Arai> only leading "_"
02:23:39: <Arai> if you compile it as C++, you'll see "0000000100000f70 T __Z12someFunctioni"
02:23:54: <noida> is it always Z12 ?
02:24:17: <Arai> they express the function's type information
02:24:32: <Arai> so, you can overload it
02:25:02: <noida> would i be able to see the c++ and c names on dxr?
02:25:15: <Arai> I guess no
02:25:40: <Arai> you'll have to calculate it, or just find it in compiled binary
02:25:52: <noida> so using XPCOM is very different from using COM?
02:26:27: <Arai> I guess COM is usable from C
02:27:09: <Arai> (as the C example in COM from js-ctypes page work) https://developer.mozilla.org/en-US/docs/Mozilla/js-ctypes/Examples/Using_COM_from_js-ctypes
02:27:10: <Arai> but I'm not sure about XPCOM
02:27:24: <Arai> if it's usable only from C++, it would be different
02:29:14: <Arai> searching the symbol name rule... it looks like hell http://en.wikipedia.org/wiki/Name_mangling#How_different_compilers_mangle_the_same_functions
02:29:38: <Arai> I thought there're relevant bug for js-ctypes
02:30:28: <Arai> ah, it's here https://bugzilla.mozilla.org/show_bug.cgi?id=770880
02:43:50: <Arai> one more message from it "as it's not yet implemented, you should have to do it yourself" ;)
02:43:52: <noida> about: http://en.wikipedia.org/wiki/Name_mangling#How_different_compilers_mangle_the_same_functions
02:44:07: <noida> couldnt we just look up what compiler ff uses and easily figure it out?
02:44:46: <Arai> I don't know if the information is embedded in binary