C++ attribute: noreturn (since C++11)

 

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Attributes

noreturn‎ (C++11)

carries_dependency (C++11)

deprecated (C++14)

fallthrough (C++17)

nodiscard (C++17)

maybe_unused (C++17)

likelyunlikely (C++20)(C++20)

no_unique_address (C++20)

assume (C++23)

optimize_for_synchronized (TM TS)

 

Indicates that the function does not return.

Syntax

[[noreturn]]

Explanation

Indicates that the function will not return control flow to the calling function after it finishes (e.g. functions that terminate the application, throw exceptions, loop indefinitely, etc.).

This attribute applies to the name of the function being declared in function declarations only. The behavior is undefined if the function with this attribute actually returns.

The first declaration of the function must specify this attribute if any declaration specifies it. If a function is declared with [[noreturn]] in one translation unit, and the same function is declared without [[noreturn]] in another translation unit, the program is ill-formed; no diagnostic required.

Example

Run this code

[[noreturn]] void f()
{
    throw "error";
    // OK
}
 
void q [[noreturn]] (int i)
{
    // behavior is undefined if called with an argument <= 0
    if (i > 0)
        throw "positive";
}
 
// void h() [[noreturn]]; // error: attribute applied to function type of h, not h itself
 
int main()
{
    try { f(); } catch(...) {}
    try { q(42); } catch(...) {}
}

Standard library

The following standard functions are declared with noreturn attribute:

Terminating functions
_Exit (C++11)	causes normal program termination without cleaning up (function)
abort	causes abnormal program termination (without cleaning up) (function)
exit	causes normal program termination with cleaning up (function)
quick_exit (C++11)	causes quick program termination without completely cleaning up (function)
terminate	function called when exception handling fails (function)
unexpected (removed in C++17)	function called when dynamic exception specification is violated (function)
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unreachable (C++23)	marks unreachable point of execution (function)
Always-throwing functions
rethrow_exception (C++11)	throws the exception from an std::exception_ptr (function)
rethrow_nested	throws the stored exception (public member function of std::nested_exception)
throw_with_nested (C++11)	throws its argument with std::nested_exception mixed in (function template)
Non-local jumps (since C++17)
longjmp	jumps to specified location (function)