Internal static variables in C, would you use them?

Question

In C you can have external static variables that are viewable every where in the file, while internal static variables are only visible in the function but is persistent

Answer 1

I find it handy for one-time, delayed, initialization:

int GetMagic()
{
   static int magicV= -1;

   if(-1 == magicV)
   {
      //do expensive, one-time initialization
      magicV = {something here}
   }
   return magicV;
}

As others have said, this isn't thread-safe during it's very first invocation, but sometimes you can get away with it :)