将 constexpr char[] var 传递给 struct 的模板参数，然后使用 fmt 到 output 会抛出异常吗？

Question

example code

template<const char* str>
class MyStruct
{
public:
    void Print()
    {
        cout << fmt::format("{}", str);
    }
};

constexpr char szTest[] = "hello";

int main()
{
    MyStruct<szTest> info;
    info.Print();
    return 0;
}

In practice, This code throws an exception in function 'basic_string_view(const Char* s)', I tried to replace constexpr with const, and then everything is ok. Does anyone know why?

I want to know why constexpr cannot be used here, Is that the rule or a bug?

More Info:

OS: Windows

IDE: vs2019 (16.11.18)

C++ Language Standard: C++20

Fmt version: 9.1.0 (The same problem exists with std::format)

Answer 1

szTest is a valid template non type argument for a parameter of type const char* and the program is well-formed.

Is that the rule or a bug?

Yes, this seems to be a msvc linker bug . Both gcc and clang execute the program without any problem.