CODEWITHSUNDEEP
c++c++14language-lawyer
xba
xba

Reputation: 177

Does static initialization order fiasco apply to block-scope static variables?

The question pretty much like in the topic, I couldn’t find clear answer to this as almost every example covers two namespace scope instances depending on each other. An example:

a.hpp

class MyGlobal {/*definition*/};
extern const MyGlobal global;

a.cpp

const MyGlobal global;

b.hpp

void myFunc();

b.cpp

extern const MyGlobal global;
class MyLocalStatic
{
    public:
    MyLocalStatic() { /* do something with global */ }
    
};

void myFunc()
{
    static MyLocalStatic s;
}

main.cpp

int main() { myFunc(); }

Let’s say that both MyGlobal and MyStaticLocal have some non-trivial constructors and so are initialized during dynamic initialization. I know that compiler can defer dynamic initialization until the variable actually used. But what if it’s not used in the same TU at all? When will compiler decide to initialize it?

Another question: if global is constant initialized I assume there’s no problem. But is it possible that s is also constant initialized (and still depends on global somehow) or this is not possible?

Would be grateful for some quotes from the standard :)

Upvotes: 1

Views: 260

Answers (1)

HolyBlackCat
HolyBlackCat

Reputation: 96012

Function-local static variables are created when control reaches their declaration for the first time. In your case it'll happen after entering main, at which point global is surely initialized.

is it possible that s is also constant initialized

Yes.

...and still depends on global somehow

Yes, only if global is constexpr.

If a variable is constant-initialized, there's nothing to worry about. There's no static-init-order fiasco at compile-time.

Upvotes: 2

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