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<functional>: unwrap move_only_function with abominable and noexcept types #5917

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<functional>: unwrap move_only_function with abominable and noexcept types #5917

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91cc747
avoid preprocessor to make the checker less messy
AlexGuteniev Nov 29, 2025
12d458b
test status quo on abominables and noexcept specifier
AlexGuteniev Nov 29, 2025
062fca7
inner function
AlexGuteniev Nov 29, 2025
2569e12
inner move_only_function
AlexGuteniev Nov 29, 2025
d6e3032
format
AlexGuteniev Nov 29, 2025
e3d13ad
-unnecessary repetitions
AlexGuteniev Nov 29, 2025
febad55
-newline
AlexGuteniev Nov 29, 2025
ffd98f8
clearer name
AlexGuteniev Nov 29, 2025
ec48ebb
avoid emitting dead code
AlexGuteniev Nov 29, 2025
d726b12
let's not pretend it's non-static
AlexGuteniev Nov 29, 2025
2c1002c
no lvalue reference
AlexGuteniev Nov 30, 2025
ed5dfc0
this part is not needed, move_only_function can't do this anyway
AlexGuteniev Nov 30, 2025
932b7ff
Merge branch 'main' into abominable
AlexGuteniev Dec 1, 2025
362c4f8
Merge branch 'main' into abominable
AlexGuteniev Dec 1, 2025
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27 changes: 23 additions & 4 deletions stl/inc/functional
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Original file line number Diff line number Diff line change
Expand Up @@ -1577,7 +1577,8 @@ _NODISCARD void* _Function_new_large(_CTypes&&... _Args) {
template <class _Rx, bool _Noexcept, class... _Types>
class _Function_base {
public:
using result_type = _Rx;
using result_type = _Rx;
using _Signature_without_cv_ref_noex = _Rx(_Types...);

struct _Impl_t { // A per-callable-type structure acting as a virtual function table.
// Using vtable emulations gives more flexibility for optimizations and reduces the amount of RTTI data.
Expand Down Expand Up @@ -2060,6 +2061,19 @@ private:
is_constructible_v<decay_t<_Fn>, initializer_list<_Ux>&, _CTypes...>
&& _Call::template _Is_callable_from<decay_t<_Fn>>;

template <class...>
friend class move_only_function;

template <class _Vt>
static constexpr bool _Is_move_only_fuction_varying_cv_ref_noex() {
if constexpr (_Is_specialization_v<_Vt, move_only_function>) {
return is_same_v<typename _Call::_Signature_without_cv_ref_noex,
typename _Vt::_Signature_without_cv_ref_noex>;
} else {
return false;
}
}

public:
using typename _Call::result_type;

Expand All @@ -2079,7 +2093,7 @@ public:
using _Vt = decay_t<_Fn>;
static_assert(is_constructible_v<_Vt, _Fn>, "_Vt should be constructible from _Fn. "
"(N4950 [func.wrap.move.ctor]/6)");
if constexpr (is_same_v<_Vt, function<_Signature...>>) {
if constexpr (is_same_v<_Vt, function<typename _Call::_Signature_without_cv_ref_noex>>) {
this->template _Construct_with_old_fn<_Vt>(_STD forward<_Fn>(_Callable));
} else {
if constexpr (is_member_pointer_v<_Vt> || is_pointer_v<_Vt>
Expand All @@ -2090,8 +2104,13 @@ public:
}
}

using _VtInvQuals = _Call::template _VtInvQuals<_Vt>;
this->template _Construct_with_fn<_Vt, _VtInvQuals>(_STD forward<_Fn>(_Callable));
if constexpr (_Is_move_only_fuction_varying_cv_ref_noex<_Vt>()) {
_Call::_Checked_move(this->_Data, _Callable._Data);
_Callable._Reset_to_null();
} else {
using _VtInvQuals = _Call::template _VtInvQuals<_Vt>;
this->template _Construct_with_fn<_Vt, _VtInvQuals>(_STD forward<_Fn>(_Callable));
}
}
}

Expand Down
40 changes: 37 additions & 3 deletions tests/std/tests/GH_005504_avoid_function_call_wrapping/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -69,12 +69,18 @@ struct copy_counter {
int count = 0;
};

using fn_type = int(copy_counter);
using fn_type = int(copy_counter);
using fn_type_r = int(copy_counter) &;
using fn_type_c = int(copy_counter) const;

#ifdef __cpp_noexcept_function_type
using fn_type_nx = int(copy_counter) noexcept;
#endif // defined(__cpp_noexcept_function_type)

struct small_callable {
const int context = 42;

int operator()(const copy_counter& counter) {
int operator()(const copy_counter& counter) const noexcept {
assert(context == 42);
return counter.count;
}
Expand All @@ -83,7 +89,7 @@ struct small_callable {
struct alignas(128) large_callable {
const int context = 1729;

int operator()(const copy_counter& counter) {
int operator()(const copy_counter& counter) const noexcept {
assert((reinterpret_cast<uintptr_t>(this) & 0x7f) == 0);
assert(context == 1729);
return counter.count;
Expand Down Expand Up @@ -156,13 +162,41 @@ int main() {
alloc_checker{0}, test_wrapped_call<move_only_function<fn_type>, move_only_function<fn_type>, small_callable>(0);
alloc_checker{1}, test_wrapped_call<move_only_function<fn_type>, move_only_function<fn_type>, large_callable>(0);

// Abominables and noexcept specifier
alloc_checker{0}, test_wrapped_call<move_only_function<fn_type_r>, move_only_function<fn_type>, small_callable>(0);
alloc_checker{1}, test_wrapped_call<move_only_function<fn_type_r>, move_only_function<fn_type>, large_callable>(0);
alloc_checker{0}, test_wrapped_call<move_only_function<fn_type>, move_only_function<fn_type_c>, small_callable>(0);
alloc_checker{1}, test_wrapped_call<move_only_function<fn_type>, move_only_function<fn_type_c>, large_callable>(0);

static_assert(!is_constructible_v<move_only_function<fn_type>, move_only_function<fn_type_r>>);
static_assert(!is_constructible_v<move_only_function<fn_type_c>, move_only_function<fn_type>>);

#ifdef __cpp_noexcept_function_type
alloc_checker{0}, test_wrapped_call<move_only_function<fn_type>, move_only_function<fn_type_nx>, small_callable>(0);
alloc_checker{1}, test_wrapped_call<move_only_function<fn_type>, move_only_function<fn_type_nx>, large_callable>(0);

static_assert(!is_constructible_v<move_only_function<fn_type_nx>, move_only_function<fn_type>>);
#endif // defined(__cpp_noexcept_function_type)

constexpr bool is_64_bit = sizeof(void*) > 4;

// Moves from function to move_only_function
alloc_checker{is_64_bit ? 0 : 1},
test_wrapped_call<move_only_function<fn_type>, function<fn_type>, small_callable>(0);
alloc_checker{1}, test_wrapped_call<move_only_function<fn_type>, function<fn_type>, large_callable>(0);

// Moves from function to abominable move_only_function
alloc_checker{is_64_bit ? 0 : 1},
test_wrapped_call<move_only_function<fn_type_r>, function<fn_type>, small_callable>(0);
alloc_checker{1}, test_wrapped_call<move_only_function<fn_type_r>, function<fn_type>, large_callable>(0);
alloc_checker{is_64_bit ? 0 : 1},
test_wrapped_call<move_only_function<fn_type_c>, function<fn_type>, small_callable>(0);
alloc_checker{1}, test_wrapped_call<move_only_function<fn_type_c>, function<fn_type>, large_callable>(0);

#ifdef __cpp_noexcept_function_type
static_assert(!is_constructible_v<move_only_function<fn_type_nx>, function<fn_type>>);
#endif // defined(__cpp_noexcept_function_type)

alloc_checker{is_64_bit ? 0 : 1},
test_wrapped_copy_call<move_only_function<fn_type>, function<fn_type>, small_callable>(0);
alloc_checker{2}, test_wrapped_copy_call<move_only_function<fn_type>, function<fn_type>, large_callable>(0);
Expand Down