There are always few little known or hidden features in each programming language. At StackOverflow.com someone started a series of posts “Hidden features of” programming languages. The Hidden Features series is great for people who are new to a certain language.

I have collected few of the features of both C and C++ here.

Like the ternary operator; most of the programmers are familiar with.

x = (y < 0) ? 10 : 20;

However this can be used the other way.

(y < 0 ? x : y) = 20;

It means the following.

if (y < 0) {
  y = 20;
}
else {
  x = 20;
}

Another feature is Resource Acquisition Is Initialization (RAII) which is often ignored by the programmers coming from non object oriented world i.e. C programming background.

Can you write a return statement in a function that returns void?

  static void foo (void) { }
  
  static void bar (void) {
    return foo(); // Note this return statement.
  }

int main (void) {
  bar();
  return 0;
}

Even you could write something like

static void foo() { return (void)"i'm discarded"; }

The comma operator isn’t widely used. It can certainly be abused, but it can also be very useful. One of the most common use is

for (int i=0; i<10; i++, doSomethingElse())
{
  /* whatever */
}

C99 has some awesome any-order structure initialization.

struct foo{
  int x;
  int y;
  char* name;
};

void main(){
  foo f = { .y = 23, .name = "awesome", .x = -38 };
}