How to Exit a Loop from Within a Switch Statement in C : Using `goto` or a Flag?

Alternative Approaches to Exiting a Loop from Within a Switch

In certain scenarios, one may encounter the need to terminate an enclosing loop from within a switch statement. While using a flag is a common approach, C provides an alternative solution: using the goto statement.

The Dilemma:

Consider the following code snippet:

<code class="cpp">while(true) {
    switch(msg->state) {
    case MSGTYPE: // ...
        break;
    // ... more stuff ...
    case DONE:
        // **HERE, I want to break out of the loop itself**
    }
}</code>

The goal is to exit the loop immediately when the msg->state equals DONE.

Using goto:

C allows the use of the goto statement to explicitly jump to a specific location in the code. This can be leveraged to achieve the desired behavior:

<code class="cpp">while ( ... ) {
    switch( ... ) {
     case ...:
         goto exit_loop;  // Jump to this location when msg->state is DONE

   }
}

exit_loop: ;  // Label for jump target</code>

In this modified code, when msg->state equals DONE, the goto statement directs the execution flow to the exit_loop label. This consequently exits both the switch and the enclosing loop.

Note: It's important to use labels (:) to identify the target of the goto statement. Using goto indiscriminately can lead to spaghetti code and maintainability issues.

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