C++ attribute: noreturn (since C++11)
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.
If a function previously declared with [[noreturn]] is invoked and that invocation eventually returns, the behavior is runtime-undefined.
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
[[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 |
|
|
(C++11) | causes normal program termination without cleaning up (function) |
| causes abnormal program termination (without cleaning up) (function) |
|
| causes normal program termination with cleaning up (function) |
|
|
(C++11) | causes quick program termination without completely cleaning up (function) |
| function called when exception handling fails (function) |
|
|
(deprecated in C++11)(removed in C++17) | function called when dynamic exception specification is violated (function) |
Compiler hints |
|
|
(C++23) | marks unreachable point of execution (function) |
Always-throwing functions |
|
|
(C++11) | throws the exception from an std::exception_ptr (function) |
| throws the stored exception (public member function of std::nested_exception) |
|
|
(C++11) | throws its argument with std::nested_exception mixed in (function template) |
Non-local jumps (since C++17) |
|
| jumps to specified location (function) |
|
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| CWG 2924 | C++11 | returning from a [[noreturn]] function would result in undefined behavior | results in runtime- undefined behavior |
References
- C++23 standard (ISO/IEC 14882:2024):
- 9.12.10 Noreturn attribute [dcl.attr.noreturn]
- C++20 standard (ISO/IEC 14882:2020):
- 9.12.9 Noreturn attribute [dcl.attr.noreturn]
- C++17 standard (ISO/IEC 14882:2017):
- 10.6.8 Noreturn attribute [dcl.attr.noreturn]
- C++14 standard (ISO/IEC 14882:2014):
- 7.6.3 Noreturn attribute [dcl.attr.noreturn]
- C++11 standard (ISO/IEC 14882:2011):
- 7.6.3 Noreturn attribute [dcl.attr.noreturn]
See also
C documentation for _Noreturn |
|
C documentation for [[noreturn]] |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/cpp/language/attributes/noreturn
