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

The best practice is to adapt a lazy approach, i.e., declare them only when you really need them ;) (and not before). It results in the following benefit:

Code is more readable if those variables are declared as near to the place of usage as possible.