An additional point which I didn't find mentioned: When functions are marked [[noreturn]], tools (not just the code-generating compiler) can use this to emit better diagnostics.

An example is when static analyzers erroneously generate warnings for dereferencing null pointers when a (custom) assert handler is used to ensure this will never happen.

void func(widget* a)

{

  my_assert(a != nullptr);

  a->apply();

}

By using the [[noreturn]] attribute on my_assert, the static_analyzer would know that a is never dereferenced if it is nullptr.

The Clang Static Analyzer has this behaviour according to its documentation (http://clang-analyzer.llvm.org/annotations.html#custom_assertions).