https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97644
--- Comment #9 from Iain Buclaw <ibuclaw at gdcproject dot org> ---
(In reply to Jan Hubicka from comment #8)
> > Current workaround I'm using locally for the time being is to call
> > thunk_info::process_early_thunks if the particular branch where this ICE
> > happens is hit.
>
> Why D frontend needs to expand the thunk early and does not rely on
> backend to handle it same way as C++ does? It would be most practical
> if both was finalizing same way.
>
> If there is good reason for not doing so and there is no PCH in D
> frontend we could just add argument to expand_thunk to avoid the game o
> putting things into a vector.
>
Not discounting that I may be doing it wrong. The call to expand_thunk is
there so that thunks for externally defined methods are generated.
As the backend usually doesn't emit such thunks, a gimple generated thunk is
forced by the frontend.
I have seen linker errors in the past when this was not done, however there
could be some alignment with what C++ does to handle this though.
A simplistic example would be:
interface I { void foo(); }
class C : I { void foo(); }
Where a TU local thunk is generated for C.foo.
A more complex example would be when interfacing with C++, where different
methods are implemented half in C++, half in D.
// C++
class Base
{
public:
virtual void base() { };
};
class Interface
{
public:
virtual int MethodCPP() = 0;
virtual int MethodD() = 0;
};
class Derived : public Base, public Interface
{
public:
int MethodCPP(); // thunk _ZThn8_N7Derived9MethodCPPEv
int MethodD(); // thunk _ZThn8_N7Derived7MethodDEv
};
int Derived::MethodCPP() { return 30; }
// D
extern (C++)
{
class Base
{
void based();
}
interface Interface
{
int MethodCPP();
int MethodD();
}
class Derived : Base, Interface
{
int MethodCPP(); // thunk _DT8_ZN7Derived9MethodCPPEv
int MethodD() // thunk _DT8_ZN7Derived7MethodDEv
{
return 3;
}
}
}
In the above, g++ and gdc give different global symbol names for the thunks, so
linker errors would occur if they are not emitted.
