Question

That is, why does this:

struct S {};

struct T
{
    T(S& s) : s{s} {}

    S& s;
};

int main()
{
    S s;
    T t{s};
}

give me a compiler error with GCC 4.7:

test.cpp: In constructor 'T::T(S&)':
test.cpp:5:18: error: invalid initialization of non-const reference of type 'S&' from an rvalue of type '<brace-enclosed initializer list>'

?

To fix the error, I have to change the s{s} to s(s). Doesn’t this break the, erm, uniformity of uniform initialization?

EDIT: I tried with clang, and clang accepts it, so perhaps it’s a GCC bug?

Answer 1

Yes, its a bug. This is something new and was voted in the working paper in February 2012 (link).

Nicol Bolas makes a good point in that gcc is actually the conforming compiler according to the FDIS approved C++11 standard because the changes to the working paper were made after that.