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

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.

Related Guidelines

Bibliography

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