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Can the constructor explainer supposedly be ignored due to the initialization form?

Consider this simple type:

struct A { A(int, int, int) {} A(std::vector<int>) {} }; /// A a({1,2,3});

The above snippet is a poorly formed program, since overload resolution fails because {1, 2, 3} can be used to initialize temporary A , so the c'tor copy is also viable to initialize A

Initially it was assumed that to solve the problem, you can use the marking of the first c'tor as explicit A(int, int, int) . And Klang agrees . On the other hand, the GCC still does not accept it , stating the same reason for the two viable c'tors.

To make matters worse, this is even more confusing for another observation. If list initialization was used instead, i.e. A a{{1,2,3}}; , then suddenly Clang and GCC accept the code with the initial definition of the class without changes (where there is nothing explicit ).

Which compiler is compatible with A a({1,2,3}); ?

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