There is already a mechanism you can use to return a different value in the case of a failure to allocate storage for a coroutine frame.

If your coroutine's promise_type provides a static function named get_return_object_on_allocation_failure then, in the case that allocating a coroutine frame fails, the invocation of the coroutine will return promise_type::get_return_object_on_allocation_failure().

Cheers,

Lewis.

On Sat, 3 Jan 2026 at 09:40, Ryan P. Nicholl via Std-Proposals <std-proposals@lists.isocpp.org> wrote:

Currently, if a coroutine function is declared noexcept, this triggers std::terminate on alloc fail.

I would like to suggest that if frame construction fails due to memory, the compiler attempts to construct a value of Ret using an instance of std::bad_alloc{} before throwing std::bad_alloc (and calling std::terminate if marked noexcept)

For example:

class coroutine_type
{
struct promise_type { ... }
private:
coroutine_type (promise_type *) { ... }
public:
coroutine_type(std::bad_alloc) {
// Handle here
}
};

This would allow declaring noexcept coroutine functions like:

coroutine_type myfunc(...) noexcept;

--
Ryan P. Nicholl
Tel: (678)-358-7765

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