Template static members initialization order

Question

I have a question related to a previous question posted here Static field initialization order Suppose I have the following struct, with 2 static members x and

Answer 1

This code is safe because Foo<double>::x has constant initialization, but Foo<double>::y has dynamic initialization.

3.6.2/2:

Constant initialization is performed:

• ...

• if an object with static or thread storage duration is not initialized by a constructor call and if every full-expression that appears in its initializer is a constant expression.

Together, zero-initialization and constant initialization are called static initialization; all other initialization is dynamic initialization. Static initialization shall be performed before any dynamic initialization takes place.

On the other hand, if you had:

double tmp = 1.1;

template <typename T>
T Foo<T>::x = tmp;

template <typename T>
T Foo<T>::y = 2.0 * Foo<T>::x;

that code would not be "safe" - Foo<double>::y could end up being either 2.2 or 0.0 (assuming nothing else modifies tmp during dynamic initializations).