Long live QT_TYPESAFE_FLAGS!
This commit adds an opt-in mechanism to kill type-unsafe functions and implicit conversions of QFlags, therefore removing an entire category of bugs that QFlags itself is supposed to protect against: QFlags<E> f; f == 3.14; // OK; f->int, int->double, then operator==(double,double) f & UnrelatedEnum; // OK if of unscoped enum, calls operator&(int) f &= 123; // calls QFlags::operator&=(int) int i = f * 42; // f->int, then operator*(int, int) Thankfully, operator+ and operator- had already been deleted. By defining QT_TYPESAFE_FLAGS one: * disables operators taking (u)int, forcing the usage of an enumeration or another QFlags object; * turns the implicit conversions towards integers/bool in explicit (one can always use fromInt/toInt instead); * adds a convenience set of (in)equality operators against literal 0, in order to keep code like `(flag & bit) == 0` compile. This set can't be added normally otherwise it would add ambiguity; * adds the unary operator~(Enum), turning it into a flag. This is a source incompatible change, in general, so it's opt-in. This is a Qt-internal macro at this point. It can't be offered to users yet because we need to fix some public API flaws first: in some places (e.g. QPainter::drawText) we ask users to do type-unsafe manipulation of flags. A user enabling the macro wouldn't be able to properly use the functions in question. This macro will be enabled in a follow-up commit. Change-Id: I796f2256b446bafc12cdcbaf7de417d12bd3619e Reviewed-by: Andrei Golubev <andrei.golubev@qt.io> Reviewed-by: Edward Welbourne <edward.welbourne@qt.io> Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
parent
a20a424066
commit
631a0cc45c
src/corelib
@ -36,6 +36,7 @@ qt_internal_add_module(Core
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EXCEPTIONS
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SOURCES
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global/archdetect.cpp
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global/qcompare_impl.h
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global/qcompare.h
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global/qcompilerdetection.h
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global/qcontainerinfo.h
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@ -45,6 +45,7 @@
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#endif
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#include <QtCore/qglobal.h>
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#include <QtCore/qcompare_impl.h>
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QT_BEGIN_NAMESPACE
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@ -65,16 +66,6 @@ enum class Uncomparable : CompareUnderlyingType
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Unordered = -127
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};
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// [cmp.categories.pre] / 3, but using a safe bool trick
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// and also rejecting std::nullptr_t (unlike the example)
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class CompareAgainstLiteralZero {
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public:
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using SafeZero = void (CompareAgainstLiteralZero::*)();
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Q_IMPLICIT constexpr CompareAgainstLiteralZero(SafeZero) noexcept {}
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template <typename T, std::enable_if_t<!std::is_same_v<T, int>, bool> = false>
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CompareAgainstLiteralZero(T) = delete;
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};
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} // namespace QtPrivate
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// [cmp.partialord]
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69
src/corelib/global/qcompare_impl.h
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69
src/corelib/global/qcompare_impl.h
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@ -0,0 +1,69 @@
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/****************************************************************************
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**
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** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
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** Contact: http://www.qt.io/licensing/
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**
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** This file is part of the QtCore module of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:LGPL$
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** Commercial License Usage
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** Licensees holding valid commercial Qt licenses may use this file in
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** accordance with the commercial license agreement provided with the
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** Software or, alternatively, in accordance with the terms contained in
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** a written agreement between you and The Qt Company. For licensing terms
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** and conditions see https://www.qt.io/terms-conditions. For further
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** information use the contact form at https://www.qt.io/contact-us.
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**
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** GNU Lesser General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU Lesser
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** General Public License version 3 as published by the Free Software
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** Foundation and appearing in the file LICENSE.LGPL3 included in the
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** packaging of this file. Please review the following information to
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** ensure the GNU Lesser General Public License version 3 requirements
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** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
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**
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** GNU General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU
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** General Public License version 2.0 or (at your option) the GNU General
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** Public license version 3 or any later version approved by the KDE Free
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** Qt Foundation. The licenses are as published by the Free Software
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** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
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** included in the packaging of this file. Please review the following
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** information to ensure the GNU General Public License requirements will
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** be met: https://www.gnu.org/licenses/gpl-2.0.html and
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** https://www.gnu.org/licenses/gpl-3.0.html.
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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#if 0
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#pragma qt_sync_skip_header_check
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#pragma qt_sync_stop_processing
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#endif
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#ifndef QCOMPARE_IMPL_H
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#define QCOMPARE_IMPL_H
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#include <QtCore/qglobal.h>
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QT_BEGIN_NAMESPACE
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namespace QtPrivate {
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// [cmp.categories.pre] / 3, but using a safe bool trick
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// and also rejecting std::nullptr_t (unlike the example)
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class CompareAgainstLiteralZero {
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public:
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using SafeZero = void (CompareAgainstLiteralZero::*)();
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Q_IMPLICIT constexpr CompareAgainstLiteralZero(SafeZero) noexcept {}
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template <typename T, std::enable_if_t<!std::is_same_v<T, int>, bool> = false>
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CompareAgainstLiteralZero(T) = delete;
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};
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} // namespace QtPrivate
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QT_END_NAMESPACE
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#endif // QCOMPARE_IMPL_H
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@ -38,6 +38,7 @@
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****************************************************************************/
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#include <QtCore/qglobal.h>
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#include <QtCore/qcompare_impl.h>
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#ifndef QFLAGS_H
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#define QFLAGS_H
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@ -115,8 +116,10 @@ public:
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constexpr static inline QFlags fromInt(Int i) noexcept { return QFlags(QFlag(i)); }
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constexpr inline Int toInt() const noexcept { return i; }
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#ifndef QT_TYPESAFE_FLAGS
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constexpr inline QFlags &operator&=(int mask) noexcept { i &= mask; return *this; }
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constexpr inline QFlags &operator&=(uint mask) noexcept { i &= mask; return *this; }
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#endif
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constexpr inline QFlags &operator&=(QFlags mask) noexcept { i &= mask.i; return *this; }
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constexpr inline QFlags &operator&=(Enum mask) noexcept { i &= Int(mask); return *this; }
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constexpr inline QFlags &operator|=(QFlags other) noexcept { i |= other.i; return *this; }
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@ -124,14 +127,27 @@ public:
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constexpr inline QFlags &operator^=(QFlags other) noexcept { i ^= other.i; return *this; }
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constexpr inline QFlags &operator^=(Enum other) noexcept { i ^= Int(other); return *this; }
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constexpr inline operator Int() const noexcept { return i; }
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#ifdef QT_TYPESAFE_FLAGS
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constexpr inline explicit operator Int() const noexcept { return i; }
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constexpr inline explicit operator bool() const noexcept { return i; }
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// For some reason, moc goes through QFlag in order to read/write
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// properties of type QFlags; so a conversion to QFlag is also
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// needed here. (It otherwise goes through a QFlags->int->QFlag
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// conversion sequence.)
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constexpr inline explicit operator QFlag() const noexcept { return QFlag(i); }
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#else
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constexpr inline Q_IMPLICIT operator Int() const noexcept { return i; }
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constexpr inline bool operator!() const noexcept { return !i; }
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#endif
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constexpr inline QFlags operator|(QFlags other) const noexcept { return QFlags(QFlag(i | other.i)); }
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constexpr inline QFlags operator|(Enum other) const noexcept { return QFlags(QFlag(i | Int(other))); }
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constexpr inline QFlags operator^(QFlags other) const noexcept { return QFlags(QFlag(i ^ other.i)); }
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constexpr inline QFlags operator^(Enum other) const noexcept { return QFlags(QFlag(i ^ Int(other))); }
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#ifndef QT_TYPESAFE_FLAGS
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constexpr inline QFlags operator&(int mask) const noexcept { return QFlags(QFlag(i & mask)); }
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constexpr inline QFlags operator&(uint mask) const noexcept { return QFlags(QFlag(i & mask)); }
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#endif
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constexpr inline QFlags operator&(QFlags other) const noexcept { return QFlags(QFlag(i & other.i)); }
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constexpr inline QFlags operator&(Enum other) const noexcept { return QFlags(QFlag(i & Int(other))); }
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constexpr inline QFlags operator~() const noexcept { return QFlags(QFlag(~i)); }
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@ -143,8 +159,6 @@ public:
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constexpr inline void operator-(Enum other) const noexcept = delete;
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constexpr inline void operator-(int other) const noexcept = delete;
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constexpr inline bool operator!() const noexcept { return !i; }
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constexpr inline bool testFlag(Enum flag) const noexcept { return testFlags(flag); }
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constexpr inline bool testFlags(QFlags flags) const noexcept { return flags.i ? ((i & flags.i) == flags.i) : i == Int(0); }
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constexpr inline bool testAnyFlag(Enum flag) const noexcept { return testAnyFlags(flag); }
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@ -167,6 +181,20 @@ public:
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friend constexpr inline bool operator!=(Enum lhs, QFlags rhs) noexcept
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{ return QFlags(lhs) != rhs; }
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#ifdef QT_TYPESAFE_FLAGS
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// Provide means of comparing flags against a literal 0; opt-in
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// because otherwise they're ambiguous against operator==(int,int)
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// after a QFlags->int conversion.
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friend constexpr inline bool operator==(QFlags flags, QtPrivate::CompareAgainstLiteralZero) noexcept
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{ return flags.i == Int(0); }
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friend constexpr inline bool operator!=(QFlags flags, QtPrivate::CompareAgainstLiteralZero) noexcept
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{ return flags.i != Int(0); }
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friend constexpr inline bool operator==(QtPrivate::CompareAgainstLiteralZero, QFlags flags) noexcept
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{ return Int(0) == flags.i; }
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friend constexpr inline bool operator!=(QtPrivate::CompareAgainstLiteralZero, QFlags flags) noexcept
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{ return Int(0) != flags.i; }
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#endif
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private:
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constexpr static inline Int initializer_list_helper(typename std::initializer_list<Enum>::const_iterator it,
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typename std::initializer_list<Enum>::const_iterator end)
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@ -183,6 +211,19 @@ private:
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typedef QFlags<Enum> Flags;
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#endif
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#ifdef QT_TYPESAFE_FLAGS
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// These are opt-in, for backwards compatibility
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#define QT_DECLARE_TYPESAFE_OPERATORS_FOR_FLAGS_ENUM(Flags) \
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constexpr inline Flags operator~(Flags::enum_type e) noexcept \
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{ return ~Flags(e); } \
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constexpr inline void operator|(Flags::enum_type f1, int f2) noexcept = delete;
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#else
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#define QT_DECLARE_TYPESAFE_OPERATORS_FOR_FLAGS_ENUM(Flags) \
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constexpr inline QIncompatibleFlag operator|(Flags::enum_type f1, int f2) noexcept \
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{ return QIncompatibleFlag(int(f1) | f2); }
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#endif
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#define Q_DECLARE_OPERATORS_FOR_FLAGS(Flags) \
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constexpr inline QFlags<Flags::enum_type> operator|(Flags::enum_type f1, Flags::enum_type f2) noexcept \
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{ return QFlags<Flags::enum_type>(f1) | f2; } \
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@ -198,12 +239,11 @@ constexpr inline void operator+(int f1, QFlags<Flags::enum_type> f2) noexcept =
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constexpr inline void operator-(Flags::enum_type f1, Flags::enum_type f2) noexcept = delete; \
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constexpr inline void operator-(Flags::enum_type f1, QFlags<Flags::enum_type> f2) noexcept = delete; \
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constexpr inline void operator-(int f1, QFlags<Flags::enum_type> f2) noexcept = delete; \
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constexpr inline QIncompatibleFlag operator|(Flags::enum_type f1, int f2) noexcept \
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{ return QIncompatibleFlag(int(f1) | f2); } \
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constexpr inline void operator+(int f1, Flags::enum_type f2) noexcept = delete; \
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constexpr inline void operator+(Flags::enum_type f1, int f2) noexcept = delete; \
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constexpr inline void operator-(int f1, Flags::enum_type f2) noexcept = delete; \
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constexpr inline void operator-(Flags::enum_type f1, int f2) noexcept = delete;
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constexpr inline void operator-(Flags::enum_type f1, int f2) noexcept = delete; \
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QT_DECLARE_TYPESAFE_OPERATORS_FOR_FLAGS_ENUM(Flags)
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QT_END_NAMESPACE
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