LWG-2762 `unique_ptr` `operator*()` should be `noexcept`

[AlexGuteniev]

LWG-2762 asks for unique_ptr and optional indirection operators to be noexcept

unique_ptr is already noexcept. It is marked as /* strengthened */ as this noexcept was not previously require by the Standard.

Note that LWG requires conditional noexcept(noexcept(*declval<pointer>()))

According to [unique.ptr.single.general]/3, unique_ptr<T, D> may obtain fancy pointer as underlying pointer type via remove_­reference_­t<D>​::​pointer.

STL/stl/inc/memory

Line 3210 in dc888f7

_NODISCARD add_lvalue_reference_t<_Ty> operator*() const noexcept /* strengthened */ {

So the fix is to change noexcept to conditional, and remove /* strengthened */ comment.

optional misses noexcept, it should be added:

STL/stl/inc/optional

Lines 345 to 381 in dc888f7

	_NODISCARD constexpr const _Ty* operator->() const {
	#if _CONTAINER_DEBUG_LEVEL > 0
	_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
	#endif // _CONTAINER_DEBUG_LEVEL > 0
	return _STD addressof(this->_Value);
	}
	_NODISCARD constexpr _Ty* operator->() {
	#if _CONTAINER_DEBUG_LEVEL > 0
	_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
	#endif // _CONTAINER_DEBUG_LEVEL > 0
	return _STD addressof(this->_Value);
	}
	_NODISCARD constexpr const _Ty& operator*() const& {
	#if _CONTAINER_DEBUG_LEVEL > 0
	_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
	#endif // _CONTAINER_DEBUG_LEVEL > 0
	return this->_Value;
	}
	_NODISCARD constexpr _Ty& operator*() & {
	#if _CONTAINER_DEBUG_LEVEL > 0
	_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
	#endif // _CONTAINER_DEBUG_LEVEL > 0
	return this->_Value;
	}
	_NODISCARD constexpr _Ty&& operator*() && {
	#if _CONTAINER_DEBUG_LEVEL > 0
	_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
	#endif // _CONTAINER_DEBUG_LEVEL > 0
	return _STD move(this->_Value);
	}
	_NODISCARD constexpr const _Ty&& operator*() const&& {
	#if _CONTAINER_DEBUG_LEVEL > 0
	_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
	#endif // _CONTAINER_DEBUG_LEVEL > 0
	return _STD move(this->_Value);
	}

These are unconditional.

[frederick-vs-ja]

Is the unconditional noexcept for unique_ptr::operator* too strong to be conforming? It seems that unique_ptr::operator* is allowed to throw an exception (from the throwing underlying operator*).

[AlexGuteniev]

Is the unconditional noexcept for unique_ptr::operator* too strong to be conforming?

Yes, already edited. Hopefully it does not require vNext