I know that in C++, I can declare variables pretty much everywhere.

I recall once reading that in C, variables must be declared at the top of a function i.e. the following is invalid:

void foo() {
  int good;
  if (...) {
    int bad;
  }
}

In the above code, is the declaraing of the bad varaible legal by C standards, or only legal due to a gcc extension?

Thanks!