Qt Creator stumbled over an issue where a connect with the new member fuction pointer based method compiled nicely but then failed at runtime with a

QObject::connect: signal not found in Foo

It is really much of a corner in this case which in addition seems to happen only with msvc. Not sure if this can be considered a compiler bug or a bug in Qt. Anyway I post this here for the records.

Scenario: A class has a signal which overrides a virtual member function of its base class. When trying to connect to the signal of the derived class from outside the library (.dll) where the two classes "live", apparently a wrong method pointer is created. The result is the above message at runtime.

Code in the library:

...
class LIBSHARED_EXPORT A : public QObject
{
public:
    virtual void foo(int) {}
};

class LIBSHARED_EXPORT B : public A
{
    Q_OBJECT
signals:
    void foo(int);
    void bar();
};
...

Code outside the library:

    ...
    B b;
    QObject::connect(&b, &B::foo, &a, &QCoreApplication::quit); // causes runtime "QObject::connect: signal not found in B"
    QObject::connect(&b, &B::bar, &a, &QCoreApplication::quit); // succeeds
    ...

See the attached msvcissue.zip for a working demo.