CODEWITHSUNDEEP
c++c++11staticthread-safety
Peter Yurkosky
Peter Yurkosky

Reputation: 11

Does the C++ "magic static" pattern work for all initialization styles?

I understand that the C++ "magic static" pattern guarantees thread-safe initialization of a local variable, since C++11. Does this hold true no matter how the local is initialized?

int some_expensive_func();

void test()
{
  static int attempt1{some_expensive_func()};
  static int attempt2 = {some_expensive_func()};
  static int attempt3 = some_expensive_func();
  static int attempt4(some_expensive_func());
}

I have an in-house static-analysis checker that's complaining about the thread-safety of the third style shown above, but I think it's OK, and I'm looking for confirmation. Thanks.

Upvotes: 0

Views: 545

Answers (1)

Brian Bi
Brian Bi

Reputation: 119164

Yes, all initialization styles are thread-safe for local static variables (since C++11). The only thing that wouldn't be thread-safe is something that's not actually an initialization, e.g., something like this:

static int x;               // zero-initialized on program startup
x = some_expensive_func();  // this is assignment, not initialization

Upvotes: 2

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