I am trying to implement a templated C-array with specialization as the following:
// template definition
template< int a, int b > constexpr int arr[] = { 1 };
// partial specialization, works ok
template< int b > constexpr double arr<0, b>[] = { 2.0 };
// full specialization, compile error in MSVC, ok in g++
template< > constexpr float arr<1, 0>[] = { 3.0f };
I am using MSVC compiler with Visual Studio 2017, with the C++ standard set to C++17, and the compiler complains that C2133: 'arr<1,0>': unknown size, so adding the size 1 to the full specialization resolves the error. However, it compiles under Ubuntu g++ 8.1.0 with -pedantic flag on.
In my opinion, full specialization on functions and classes acts as if a non-template version is defined, so I guess this should also apply to the variable template, and the full specialization above could be equivalent to (except for the name)
constexpr float arr_with_a1_and_b0[] = { 3.0f };
which looks pretty valid to me, since the size should be deduced from the list-initialization (aggregate-initialization).
My question is: Is the code above valid C++? Which compiler is correct?
