Difference between revisions of "cpp/language/attributes/noreturn"

Revision as of 11:15, 12 August 2024

Indicates that the function does not return.

Syntax

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

[[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:

References