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struct T
{
    int a;
};
 
struct C
{
    T& r;
    C(T& v) : r(v) {}
};
 
struct E : T
{
    T& r;
    E(T const& v) : r(*this), T(v) {}   // ok
};
 
struct F : C, T // base order doesn't matter here
{
    F(T const& v) : C(*this), T(v) {}   // error : C::r is not initialized properly
    //F(T const& v) : C(*static_cast<T*>(this)), T(v) {}   // ok
    //F(T const& v) : C(static_cast<T&>(*this)), T(v) {}   // ok
};
 
int main()
{
    T v;
    F f(v);
    f.r.a = 1;
}

prog.cpp: In constructor 'F::F(const T&)':
prog.cpp:20:34: error: call of overloaded 'C(F&)' is ambiguous
prog.cpp:9:5: note: candidates are: C::C(T&)
prog.cpp:7:1: note:                 C::C(const C&)

Standard output is empty