How to execute a piece of code only once?

Question

I have an application which has several functions in it. Each function can be called many times based on user input. However I need to execute a small segment of the code wi

Answer 1

Use global static objects with constructors (which are called before main)? Or just inside a routine

static bool initialized;
if (!initialized) {
   initialized = true;
   // do the initialization part
}

There are very few cases when this is not fast enough!

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addenda

In multithreaded context this might not be enough:

You may also be interested in pthread_once or constructor function __attribute__ of GCC.

With C++11, you may want std::call_once.

You may want to use and perhaps declare static volatile std::atomic_bool initialized; (but you need to be careful) if your function can be called from several threads.

^{But these might not be available on your system; they are available on Linux!}