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QObject: remove the operator comma hack

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It was the easiest way to implement this back in the day without an
explosion of combinatorics.

Change-Id: Ia930b1a2ed1e465a826ffffd179c5bb4657d0562
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
This commit is contained in:
Thiago Macieira 2023-11-30 10:13:09 +01:00
parent a337b8360f
commit f894f04c9d
1 changed files with 47 additions and 29 deletions
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76
src/corelib/kernel/qobjectdefs_impl.h
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@ -51,25 +51,27 @@ namespace QtPrivate {
template <typename L> struct List_Left<L, 0> { typedef List<> Value; };
/*
Trick to set the return value of a slot that works even if the signal or the slot returns void
to be used like
function(), ApplyReturnValue<ReturnType>(&return_value)
if function() returns a value, the operator,(T, ApplyReturnValue<ReturnType>) is called, but if it
returns void, the built-in one is used without an error.
*/
template <typename T>
struct ApplyReturnValue {
void *data;
explicit ApplyReturnValue(void *data_) : data(data_) {}
This is used to store the return value from a slot, whether the caller
wants to store this value (QMetaObject::invokeMethod() with
qReturnArg() or non-void signal ) or not.
*/
struct FunctorCallBase
{
template <typename R, typename Lambda>
static void call_internal(void **args, Lambda &&fn) noexcept(noexcept(fn()))
{
using SlotRet = decltype(fn());
if constexpr (std::is_void_v<R> || std::is_void_v<SlotRet>) {
Q_UNUSED(args);
} else {
if (args[0]) {
*reinterpret_cast<R *>(args[0]) = fn();
return;
}
}
fn();
}
};
template<typename T, typename U>
void operator,(T &&value, const ApplyReturnValue<U> &container) {
if (container.data)
*reinterpret_cast<U *>(container.data) = std::forward<T>(value);
}
template<typename T>
void operator,(T, const ApplyReturnValue<void> &) {}
/*
The FunctionPointer<Func> struct is a type trait for function pointer.
@ -132,41 +134,57 @@ namespace QtPrivate {
template <typename, typename, typename, typename> struct FunctorCall;
template <int... II, typename... SignalArgs, typename R, typename Function>
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, Function> {
static void call(Function &f, void **arg) {
f((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, Function> : FunctorCallBase
{
static void call(Function &f, void **arg)
{
call_internal<R>(arg, [&] {
return f((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...);
});
}
};
template <int... II, typename... SignalArgs, typename R, typename... SlotArgs, typename SlotRet, class Obj>
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...)> {
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...)> : FunctorCallBase
{
static void call(SlotRet (Obj::*f)(SlotArgs...), Obj *o, void **arg)
{
assertObjectType<Obj>(o);
(o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
call_internal<R>(arg, [&] {
return (o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...);
});
}
};
template <int... II, typename... SignalArgs, typename R, typename... SlotArgs, typename SlotRet, class Obj>
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...) const> {
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...) const> : FunctorCallBase
{
static void call(SlotRet (Obj::*f)(SlotArgs...) const, Obj *o, void **arg)
{
assertObjectType<Obj>(o);
(o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
call_internal<R>(arg, [&] {
return (o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...);
});
}
};
template <int... II, typename... SignalArgs, typename R, typename... SlotArgs, typename SlotRet, class Obj>
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...) noexcept> {
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...) noexcept> : FunctorCallBase
{
static void call(SlotRet (Obj::*f)(SlotArgs...) noexcept, Obj *o, void **arg)
{
assertObjectType<Obj>(o);
(o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
call_internal<R>(arg, [&]() noexcept {
return (o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...);
});
}
};
template <int... II, typename... SignalArgs, typename R, typename... SlotArgs, typename SlotRet, class Obj>
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...) const noexcept> {
struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...) const noexcept> : FunctorCallBase
{
static void call(SlotRet (Obj::*f)(SlotArgs...) const noexcept, Obj *o, void **arg)
{
assertObjectType<Obj>(o);
(o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
call_internal<R>(arg, [&]() noexcept {
return (o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...);
});
}
};