bugprone-dynamic-static-initializers

Finds instances of static variables that are dynamically initialized in header files.

This can pose problems in certain multithreaded contexts. For example, when disabling compiler generated synchronization instructions for static variables initialized at runtime (e.g. by -fno-threadsafe-statics), even if a particular project takes the necessary precautions to prevent race conditions during initialization by providing their own synchronization, header files included from other projects may not. Therefore, such a check is helpful for ensuring that disabling compiler generated synchronization for static variable initialization will not cause problems.

Consider the following code:

int foo() {
  static int k = bar();
  return k;
}

When synchronization of static initialization is disabled, if two threads both call foo for the first time, there is the possibility that k will be double initialized, creating a race condition.