Static const declaration, constexpr definition of variable, valid c++?

Question

Example: In header file:

class Foo
{
     static const int IntArray[];                         
};

In source file:

constexp         


        

Answer 1

I doubt it's compliant. The declaration and definition are required to be identical AFAIK.

It's certainly not portable. Although gcc, clang and microsoft cl 2017 accept it,

ICC reports:

(6): error: member "Foo::IntArray" (declared at line 3) was previously not declared constexpr
  constexpr int Foo::IntArray[] = { 1, 2, 3, 4 };
  ^
compilation aborted for  (code 2)
Compiler exited with result code 2