MSC55-CPP. Do not return from a function declared [[noreturn]]

The [[noreturn]] attribute specifies that a function does not return. The C++ Standard, [dcl.attr.noreturn] paragraph 2 [ISO/IEC 14882-2014], states:

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

A function that specifies [[noreturn]] can prohibit returning by throwing an exception, entering an infinite loop, or calling another function designated with the [[noreturn]] attribute.

Noncompliant Code Example

In this noncompliant code example, if the value 0 is passed, control will flow off the end of the function, resulting in an implicit return and undefined behavior:

#include <cstdlib>
 
[[noreturn]] void f(int i) {
  if (i > 0)
    throw "Received positive input";
  else if (i < 0)
    std::exit(0);
}

Compliant Solution

In this compliant solution, the function does not return on any code path:

#include <cstdlib>
 
[[noreturn]] void f(int i) {
  if (i > 0)
    throw "Received positive input";
  std::exit(0);
}

Risk Assessment

Returning from a function marked [[noreturn]] results in undefined behavior that might be exploited to cause data integrity violations.

Automated Detection

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Bibliography