# V1082. Function marked as 'noreturn' may return control. This will result in undefined behavior.

The analyzer has detected a function marked as 'noreturn'. One or more execution branches of this function nevertheless may return control flow.

First, let's look at the correct example:

    [[ noreturn ]] void q() {
      throw "error"; // OK
    }

The 'q' function throws an exception and then terminates. Further, the program execution is passed to the exception handler, and doesn't return to the 'q' function's caller. At the same time, the compiler understands that the code following the call of the 'q' function is unreachable and it can be optimized.

    [[ noreturn ]] void f(int i) { // behavior is undefined
                                   // if called with an argument <= 0
      if (i > 0)
        throw "positive";
    }

The same thing happens when the 'f' function is called with a positive argument value. However, if a negative value or zero is passed to the 'f' function during the program execution, an undefined behavior will occur according to the C++ standard:

> 9.12.9 Noreturn attribute [dcl.attr.noreturn]

> 2. If a function f is called where f was previously declared with the noreturn attribute and f eventually returns, the behavior is undefined.

This diagnostic is classified as:

CERT-MSC53-CPP