> When I am trying to build Mozilla with gcc-mingw, I came across
> the linkage error of undefined symbols in multiple inheritance case.
> And I have made a simple test case to reproduce the problem. But the
> test case is still very complex, I think. So, I came down to find the
> what are the real problems. And now, I think I have, so I just
> describe what I found here:
>
> For a class hierarchy :
>
> class SuperSuperBase {
> public:
> SuperSuperBase();
> ~SuperSuperBase();
>
> virtual void __attribute__((__stdcall__)) funcSSB() = 0;
> };
>
> class SuperBase : public SuperSuperBase {
> public:
> SuperBase();
> ~SuperBase();
>
> virtual void __attribute__((__stdcall__)) funcSB() = 0;
> };
>
> class Base : public SuperBase {
> public:
> Base();
> ~Base();
>
> virtual void __attribute__((__stdcall__)) funcB() = 0;
> };
>
> class ChildA: public Base {
> public:
> ChildA();
> ~ChildA();
>
> virtual void __attribute__((__stdcall__)) funcCA() = 0;
> };
>
> class ChildB: public SuperBase {
> public:
> ChildB();
> ~ChildB();
>
> virtual void __attribute__((__stdcall__)) funcCB() = 0;
> };
>
> class DLL Child : public ChildA,
> public ChildB {
> public:
> Child();
> ~Child();
>
> virtual void __attribute__((__stdcall__)) funcSSB();
> virtual void __attribute__((__stdcall__)) funcSB();
> virtual void __attribute__((__stdcall__)) funcB();
> virtual void __attribute__((__stdcall__)) funcCB();
> virtual void __attribute__((__stdcall__)) funcCA();
> };
>
> I make the Child in a DLL and then I import it from the DLL to build a
> test application. But I failed with the undefined symbols of
> "funcSSB,funcSB,funcCB".
> And the errors occurs when I build with gcc 4.3.0 but not with gcc
> 3.4.2. So, I use i686-mingw32-nm to dump the object file which
> contains the definition of the Child class. And for the three
> undefined functions, the two compiler output different symbols,
> Gcc 3.4.2:
> U __ZTVN10__cxxabiv117__class_type_infoE
> U __ZTVN10__cxxabiv120__si_class_type_infoE
> U __ZTVN10__cxxabiv121__vmi_class_type_infoE
> 00000000 T [EMAIL PROTECTED]
> 00000000 T [EMAIL PROTECTED]
> 00000000 T [EMAIL PROTECTED]
>
> Gcc 4.3.0:
> U __ZTVN10__cxxabiv117__class_type_infoE
> U __ZTVN10__cxxabiv120__si_class_type_infoE
> U __ZTVN10__cxxabiv121__vmi_class_type_infoE
> 00000306 T __ZThn4_N5Child6funcCBEv
> U [EMAIL PROTECTED]
> 000002d7 T __ZThn4_N5Child6funcSBEv
> U [EMAIL PROTECTED]
> 000002c8 T __ZThn4_N5Child7funcSSBEv
> U [EMAIL PROTECTED]
>
> I think the difference here is the key point of the linkage error.
> Could anybody help to give some more insight here? Any advice will be
> appreciated very much!
Could anybody give some advice on this? Thanks!
Regards!
Bo
