assigned to @majnemer

Here's a slightly saner reduction:

class A {};
template class B {
void (T::*mCallOnResume)();
};
class C : A, B {
};

C p;

As a workaround, you can do this:

class A {};
template class B {
void (T::*mCallOnResume)();
};
class __multiple_inheritance C; // workaround
class C : A, B {
};

Our diagnostic is bad, but here's what's happening:

• We parse C's base specifiers
• Instantiate B
• RequireCompleteType on 'void (C::*)()'
• RequireCompleteType on C, lock in the inheritance model, probably as single inheritance, because we haven't set C's base specifiers yet
• Finish C's definition, realize that we assumed C was using single inheritance when it really used multiple inheritance.

Thanks a lot for the analysis and workaround, Reid! I'll try to work with Jeff tomorrow to see how we can apply this workaround to our code. I have to admit that I don't entirely understand the implications of these MSVC keywords (I just learned about their existence yesterday.) I assume the workaround won't change how the code will behave when built with cl?

marginally reduced:
template
class A {
int T::*x;
};
class B : virtual A {};

Fixed in r210886.

I should point out that while we have fixed this in clang, note that sizeof(mCallOnResume) will probably be 16 (1 pointer and 3 ints!) on x86 with both MSVC and Clang. That's probably larger than you wanted. The __multiple_inheritance workaround that I gave should make it just 8 (1 pointer and 1 int).

It seems the fix is not 100% correct.
We are using clang through libTooling, -v gives:
clang version 3.6.0 (branches/release_36 230502) (llvm/branches/release_36 230501).

code (simplified) :
class A : public B<wchar_t>
{
public:
// ...
typedef bool (A::*C)(const D<wchar_t>&, E&, int, const F&);
// ...
static C m[];
// ...
};

clang output:
In file included from ...
...
a.h:95:1: error: inheritance model does not match definition
class A : public B<wchar_t>
^
a.h:95:7: note: A defined here
class A : public B<wchar_t>
^
1 error generated.
Error while processing ....cpp.

József, I cannot reproduce with what you have posted. Please provide a complete example.