[utility.undefined]

22 General utilities library [utilities]

22.2 Utility components [utility]

22.2.9 Undefined behavior [utility.undefined]

[[noreturn]] void unreachable();

Preconditions: false is true.

[Note 1:

This precondition cannot be satisfied, thus the behavior of calling unreachable is undefined.

— end note]

[Example 1: int f(int x) { switch (x) { case 0: case 1: return x; default: std::unreachable(); } } int a = f(1); // OK, a has value 1 int b = f(3); // undefined behavior — end example]

void observable_checkpoint() noexcept;