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Implement LWG-3900 The allocator_arg_t overloads of generator::promise_type::operator new should not be constrained #5150

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Implement LWG-3900 The allocator_arg_t overloads of generator::promise_type::operator new should not be constrained #5150

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b987293
Implement LWG-3900
frederick-vs-ja Nov 26, 2024
b81a439
Modify test coverage
frederick-vs-ja Nov 26, 2024
8bee168
Refer to WG21-N5001
frederick-vs-ja Dec 18, 2024
3baedfe
Merge branch 'main' into lwg-3900
frederick-vs-ja Dec 18, 2024
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6 changes: 4 additions & 2 deletions stl/inc/generator
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Original file line number Diff line number Diff line change
Expand Up @@ -110,16 +110,18 @@ namespace _Gen_detail {
}

template <class _Alloc2, class... _Args>
requires convertible_to<const _Alloc2&, _Proto_allocator>
_NODISCARD_RAW_PTR_ALLOC static void* operator new(
const size_t _Size, allocator_arg_t, const _Alloc2& _Al, const _Args&...) {
static_assert(convertible_to<const _Alloc2&, _Proto_allocator>,
"argument convertible to the allocator type is required");
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return _Allocate(static_cast<_Alloc>(static_cast<_Proto_allocator>(_Al)), _Size);
}

template <class _This, class _Alloc2, class... _Args>
requires convertible_to<const _Alloc2&, _Proto_allocator>
_NODISCARD_RAW_PTR_ALLOC static void* operator new(
const size_t _Size, const _This&, allocator_arg_t, const _Alloc2& _Al, const _Args&...) {
static_assert(convertible_to<const _Alloc2&, _Proto_allocator>,
"argument convertible to the allocator type is required");
return _Allocate(static_cast<_Alloc>(static_cast<_Proto_allocator>(_Al)), _Size);
}

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10 changes: 4 additions & 6 deletions tests/std/tests/P2502R2_generator_promise/test.cpp
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Expand Up @@ -78,20 +78,18 @@ void test_operator_new(typename Gen::promise_type& p, const Alloc2& alloc2 = {})
}

// Test 'operator new(size_t, allocator_arg_t, const Alloc2&, const Args&...)'
constexpr bool has_op_new2 = HasOperatorNew<Promise, size_t, allocator_arg_t, const Alloc2&, int, int>;
static_assert(has_op_new2 == (same_as<Alloc, void> || convertible_to<const Alloc2&, Alloc>) );
if constexpr (has_op_new2) {
// This operator new is unconstrained.
if constexpr (same_as<Alloc, void> || convertible_to<const Alloc2&, Alloc>) {
const size_t size = __STDCPP_DEFAULT_NEW_ALIGNMENT__;
void* const mem = p.operator new(size, allocator_arg, alloc2, 0, 0);
assert(reinterpret_cast<uintptr_t>(mem) % __STDCPP_DEFAULT_NEW_ALIGNMENT__ == 0);
p.operator delete(mem, size);
}

// Test 'operator new(size_t, const This&, allocator_arg_t, const Alloc2&, const Args&...)'
// This operator new is unconstrained.
struct S {};
constexpr bool has_op_new3 = HasOperatorNew<Promise, size_t, const S&, allocator_arg_t, const Alloc2&, int, int>;
static_assert(has_op_new3 == (same_as<Alloc, void> || convertible_to<const Alloc2&, Alloc>) );
if constexpr (has_op_new3) {
if constexpr (same_as<Alloc, void> || convertible_to<const Alloc2&, Alloc>) {
const size_t size = __STDCPP_DEFAULT_NEW_ALIGNMENT__;
const S s;
void* const mem = p.operator new(size, s, allocator_arg, alloc2, 0, 0);
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