c++ - Are static variables inlined by default inside templates in C++17? -

are static variables inlined default inside templates in c++17? here's example:

template<typename t> struct someclass {     static t test; };  struct someclass2 {     static constexpr int test = 9; }; 

are variables inlined or still need out of line definition odr used?

a static constexpr implicitly inline, otherwise need mark inline

template<typename t> struct someclass {     inline static t test; // inline };  struct someclass2 {     static constexpr int test = 9; // inline }; 

cfr. n4606 [depr.static_constexpr]

for compatibility prior c++ international standards, constexpr static data member may redundantly redeclared outside class no initializer. usage deprecated.

example:

struct {   static constexpr int n = 5; // definition (declaration in c++ 2014) }; const int a::n; // redundant declaration (definition in c++ 2014) 

and [dcl.constexpr] (barry beat me it)

a function or static data member declared constexpr specifier implicitly inline function or variable (7.1.6).