Is declaration of variables expensive?

Question

While coding in C, I came across the below situation.

int function ()
{
  if (!somecondition) return false;

  internalStructure  *str1;
  internalStructure *str         


        

Answer 1

I prefer keeping the "early out" condition at the top of the function, in addition to documenting why we are doing it. If we put it after a bunch of variable declarations, someone not familiar with the code could easily miss it, unless they know they have to look for it.

Documenting the "early out" condition alone is not always sufficient, it is better to make it clear in the code as well. Putting the early out condition at the top also makes it easier to keep the document in sync with the code, for instance, if we later decide to remove the early out condition, or to add more such conditions.