diff options
author | Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> | 2020-02-15 00:11:22 +0100 |
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committer | Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> | 2020-06-10 16:49:08 +0200 |
commit | 8e98a161e993c6636d217276a0f2373d642ff050 (patch) | |
tree | 23adce823bfab9795cf7b775d35f14be7baedc10 /src/corelib/tools/qpair.h | |
parent | ce5931aaf2c9698925366e787d08747a1c60c378 (diff) |
Long live std::pair!
Make QPair an alias for std::pair, and qMakePair just a forwarder
towards std::make_pair.
Why? Fundamentally to ditch a bunch of NIH code; gain for free
structured bindings, std::tuple and std::reference_wrapper
compatibility, and so on.
Breakages:
* Some that code manually forward declares QPair.
We don't care about it (<QContainerFwd> is the proper way).
* Some code that overloads on std::pair and QPair. Luckily
it's mostly centralized: debug, metatypes, testing macros.
Just remove the QPair overload.
* Usages of qMakePair forcing the template type parameters.
There are a handful of these in qtbase, but only one was actually
broken.
* std::pair is NOT (and will never likely be) trivially copiable.
This is agreed to be a mistake done by practically all implementations
in C++11, can can't be fixed without breaking ABI.
Some code using QPair assuming it's trivially copiable may break;
exactly one occurrence was in qtbase.
* QMetaType logic extracts the type names in two different ways,
one by looking at the source code string (e.g. extracted by moc)
and one via some ad-hoc reflection in C++. We need to make
"QPair" (as spelled in the source code) be the same as "std::pair"
(gathered via reflection, which will see through the alias)
when compared. The way it's already done e.g. for QList is
by actually replacing the moc-extracted name with the name
of the actual type used in C++; do the same here.
On libc++, std::pair is actually in an inline namespace --
i.e. std::__1::pair; the reflection will extract and store
"std::__1::pair" so we need an ad-hoc fix to QMetaType.
[ChangeLog][QtCore][QPair] QPair is now an alias to std::pair,
and does not exist as a class in Qt any more. This may break
code such as functions overloaded for both QPair and std::pair.
Usually, the overload taking a QPair can be safely discarded,
leaving only the one taking a std::pair. QPair API has not changed,
and qMakePair is still available for compatibility (although
new code is encouraged to use std::pair and std::make_pair
directly instead).
Change-Id: I7725c751bf23946cde577b1406e86a336c0a3dcf
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Diffstat (limited to 'src/corelib/tools/qpair.h')
-rw-r--r-- | src/corelib/tools/qpair.h | 111 |
1 files changed, 9 insertions, 102 deletions
diff --git a/src/corelib/tools/qpair.h b/src/corelib/tools/qpair.h index 9ebf88bc8f..6cb7fc5079 100644 --- a/src/corelib/tools/qpair.h +++ b/src/corelib/tools/qpair.h @@ -44,115 +44,22 @@ QT_BEGIN_NAMESPACE - -template <class T1, class T2> -struct QPair -{ - typedef T1 first_type; - typedef T2 second_type; - - Q_DECL_CONSTEXPR QPair() - noexcept((std::is_nothrow_default_constructible<T1>::value && - std::is_nothrow_default_constructible<T2>::value)) - : first(), second() {} - Q_DECL_CONSTEXPR QPair(const T1 &t1, const T2 &t2) - noexcept((std::is_nothrow_copy_constructible<T1>::value && - std::is_nothrow_copy_constructible<T2>::value)) - : first(t1), second(t2) {} - // compiler-generated copy/move ctor/assignment operators are fine! - - template <typename TT1, typename TT2> - Q_DECL_CONSTEXPR QPair(const QPair<TT1, TT2> &p) - noexcept((std::is_nothrow_constructible<T1, TT1&>::value && - std::is_nothrow_constructible<T2, TT2&>::value)) - : first(p.first), second(p.second) {} - template <typename TT1, typename TT2> - Q_DECL_RELAXED_CONSTEXPR QPair &operator=(const QPair<TT1, TT2> &p) - noexcept((std::is_nothrow_assignable<T1, TT1&>::value && - std::is_nothrow_assignable<T2, TT2&>::value)) - { first = p.first; second = p.second; return *this; } - template <typename TT1, typename TT2> - Q_DECL_CONSTEXPR QPair(QPair<TT1, TT2> &&p) - noexcept((std::is_nothrow_constructible<T1, TT1>::value && - std::is_nothrow_constructible<T2, TT2>::value)) - // can't use std::move here as it's not constexpr in C++11: - : first(static_cast<TT1 &&>(p.first)), second(static_cast<TT2 &&>(p.second)) {} - template <typename TT1, typename TT2> - Q_DECL_RELAXED_CONSTEXPR QPair &operator=(QPair<TT1, TT2> &&p) - noexcept((std::is_nothrow_assignable<T1, TT1>::value && - std::is_nothrow_assignable<T2, TT2>::value)) - { first = std::move(p.first); second = std::move(p.second); return *this; } - - Q_DECL_RELAXED_CONSTEXPR void swap(QPair &other) - noexcept(noexcept(qSwap(other.first, other.first)) && noexcept(qSwap(other.second, other.second))) - { - // use qSwap() to pick up ADL swaps automatically: - qSwap(first, other.first); - qSwap(second, other.second); - } - - T1 first; - T2 second; -}; - -#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201606 -template<class T1, class T2> -QPair(T1, T2) -> QPair<T1, T2>; +#if 0 +#pragma qt_class(QPair) #endif template <typename T1, typename T2> -void swap(QPair<T1, T2> &lhs, QPair<T1, T2> &rhs) noexcept(noexcept(lhs.swap(rhs))) -{ lhs.swap(rhs); } - -// mark QPair<T1,T2> as complex/movable/primitive depending on the -// typeinfos of the constituents: -template<class T1, class T2> -class QTypeInfo<QPair<T1, T2> > : public QTypeInfoMerger<QPair<T1, T2>, T1, T2> {}; // Q_DECLARE_TYPEINFO +using QPair = std::pair<T1, T2>; -template <class T1, class T2> -Q_DECL_CONSTEXPR Q_INLINE_TEMPLATE bool operator==(const QPair<T1, T2> &p1, const QPair<T1, T2> &p2) - noexcept(noexcept(p1.first == p2.first && p1.second == p2.second)) -{ return p1.first == p2.first && p1.second == p2.second; } - -template <class T1, class T2> -Q_DECL_CONSTEXPR Q_INLINE_TEMPLATE bool operator!=(const QPair<T1, T2> &p1, const QPair<T1, T2> &p2) - noexcept(noexcept(!(p1 == p2))) -{ return !(p1 == p2); } - -template <class T1, class T2> -Q_DECL_CONSTEXPR Q_INLINE_TEMPLATE bool operator<(const QPair<T1, T2> &p1, const QPair<T1, T2> &p2) - noexcept(noexcept(p1.first < p2.first || (!(p2.first < p1.first) && p1.second < p2.second))) -{ - return p1.first < p2.first || (!(p2.first < p1.first) && p1.second < p2.second); -} - -template <class T1, class T2> -Q_DECL_CONSTEXPR Q_INLINE_TEMPLATE bool operator>(const QPair<T1, T2> &p1, const QPair<T1, T2> &p2) - noexcept(noexcept(p2 < p1)) -{ - return p2 < p1; -} - -template <class T1, class T2> -Q_DECL_CONSTEXPR Q_INLINE_TEMPLATE bool operator<=(const QPair<T1, T2> &p1, const QPair<T1, T2> &p2) - noexcept(noexcept(!(p2 < p1))) -{ - return !(p2 < p1); -} - -template <class T1, class T2> -Q_DECL_CONSTEXPR Q_INLINE_TEMPLATE bool operator>=(const QPair<T1, T2> &p1, const QPair<T1, T2> &p2) - noexcept(noexcept(!(p1 < p2))) +template <typename T1, typename T2> +constexpr decltype(auto) qMakePair(T1 &&value1, T2 &&value2) + noexcept(noexcept(std::make_pair(std::forward<T1>(value1), std::forward<T2>(value2)))) { - return !(p1 < p2); + return std::make_pair(std::forward<T1>(value1), std::forward<T2>(value2)); } -template <class T1, class T2> -Q_DECL_CONSTEXPR Q_OUTOFLINE_TEMPLATE QPair<T1, T2> qMakePair(const T1 &x, const T2 &y) - noexcept(noexcept(QPair<T1, T2>(x, y))) -{ - return QPair<T1, T2>(x, y); -} +template<class T1, class T2> +class QTypeInfo<std::pair<T1, T2>> : public QTypeInfoMerger<std::pair<T1, T2>, T1, T2> {}; QT_END_NAMESPACE |