CODEWITHSUNDEEP
c++
Dean
Dean

Reputation: 6950

Static variable initialized with another one

I'm aware of the static order initialization fiasco, but I'm wondering if the following would also trigger it:

const static Point center = CalculateCenter();
static Point currentPoint = center;

I'd like to have two static variables (internal linkage in a TU), one is initialized and constant, the other one is shared across a great deal of instances but at first it should have the same value of center.

Would this trigger static order initialization fiasco? If it does, how should I code this instead?

Upvotes: 0

Views: 56

Answers (3)

El pupi
El pupi

Reputation: 458

As the previous answer said, in the same translation unit there is no problem. The order is preserved.

If the two static variables are not in the same translation unit you should use function instead as follow:

//somewhere in a class X
static const Point& center() { const static Point _center = CalculateCenter(); return _center; }

//somewhere in a class Y
static Point& currentPoint() { static Point _current_point = X::center(); return _current_point; }

Then when you need the variables you use the function accessors X::center() or Y::currentPoint().

Upvotes: 2

Rakete1111
Rakete1111

Reputation: 48928

If they are all in the same compilation unit, then it's fine (if you order them correctly). But if they're not, then it's undefined behavior, because of the initialization order. You could however declare center as constexpr instead of const, then center is known at compile time which should be ok, but then CalculateCenter() would also need to be a constexpr, which is maybe not possible in your case.

Upvotes: 3

bottaio
bottaio

Reputation: 5073

It is clearly defined that within one compilation unit the order is well defined and it follows declaration order. The problem appears across different units which is not a case here so the code is totally fine.

Upvotes: 3

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