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Constrain the data stream operators for containers

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Check that we can successfully instantiate the data
stream operator for a container before we actually try.

This is required so we can automate registration of debug
stream operators with QMetaType.

Change-Id: Ib100a5242470d7fc8067058cc4d81af2fa9354b0
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
This commit is contained in:
Lars Knoll 2020-07-06 14:06:08 +02:00
parent 8ad9e81694
commit 3ef8ec2ee1
4 changed files with 46 additions and 18 deletions
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11
src/corelib/global/qtypeinfo.h
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@ -464,6 +464,17 @@ struct has_ostream_operator<Stream, T, std::void_t<decltype(detail::reference<St
template <typename Stream, typename T> template <typename Stream, typename T>
constexpr bool has_ostream_operator_v = has_ostream_operator<Stream, T>::value; constexpr bool has_ostream_operator_v = has_ostream_operator<Stream, T>::value;
template <typename Stream, typename, typename = void>
struct has_istream_operator : std::false_type {};
template <typename Stream, typename T>
struct has_istream_operator<Stream, T, std::void_t<decltype(detail::reference<Stream>() >> detail::reference<T>())>>
: std::true_type {};
template <typename Stream, typename T>
constexpr bool has_istream_operator_v = has_istream_operator<Stream, T>::value;
template <typename Stream, typename T>
constexpr bool has_stream_operator_v = has_ostream_operator_v<Stream, T> && has_istream_operator_v<Stream, T>;
} }

35
src/corelib/serialization/qdatastream.h
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@ -347,6 +347,13 @@ QDataStream &writeAssociativeMultiContainer(QDataStream &s, const Container &c)
} // QtPrivate namespace } // QtPrivate namespace
template<typename ...T>
using QDataStreamIfHasOStreamOperators =
std::enable_if_t<std::conjunction_v<QTypeTraits::has_ostream_operator<QDataStream, T>...>, QDataStream &>;
template<typename ...T>
using QDataStreamIfHasIStreamOperators =
std::enable_if_t<std::conjunction_v<QTypeTraits::has_istream_operator<QDataStream, T>...>, QDataStream &>;
/***************************************************************************** /*****************************************************************************
QDataStream inline functions QDataStream inline functions
*****************************************************************************/ *****************************************************************************/
@ -406,88 +413,88 @@ operator>>(QDataStream &s, T &t)
{ return s >> reinterpret_cast<typename std::underlying_type<T>::type &>(t); } { return s >> reinterpret_cast<typename std::underlying_type<T>::type &>(t); }
template<typename T> template<typename T>
inline QDataStream &operator>>(QDataStream &s, QList<T> &v) inline QDataStreamIfHasIStreamOperators<T> operator>>(QDataStream &s, QList<T> &v)
{ {
return QtPrivate::readArrayBasedContainer(s, v); return QtPrivate::readArrayBasedContainer(s, v);
} }
template<typename T> template<typename T>
inline QDataStream &operator<<(QDataStream &s, const QList<T> &v) inline QDataStreamIfHasOStreamOperators<T> operator<<(QDataStream &s, const QList<T> &v)
{ {
return QtPrivate::writeSequentialContainer(s, v); return QtPrivate::writeSequentialContainer(s, v);
} }
template <typename T> template <typename T>
inline QDataStream &operator>>(QDataStream &s, QSet<T> &set) inline QDataStreamIfHasIStreamOperators<T> operator>>(QDataStream &s, QSet<T> &set)
{ {
return QtPrivate::readListBasedContainer(s, set); return QtPrivate::readListBasedContainer(s, set);
} }
template <typename T> template <typename T>
inline QDataStream &operator<<(QDataStream &s, const QSet<T> &set) inline QDataStreamIfHasOStreamOperators<T> operator<<(QDataStream &s, const QSet<T> &set)
{ {
return QtPrivate::writeSequentialContainer(s, set); return QtPrivate::writeSequentialContainer(s, set);
} }
template <class Key, class T> template <class Key, class T>
inline QDataStream &operator>>(QDataStream &s, QHash<Key, T> &hash) inline QDataStreamIfHasIStreamOperators<Key, T> operator>>(QDataStream &s, QHash<Key, T> &hash)
{ {
return QtPrivate::readAssociativeContainer(s, hash); return QtPrivate::readAssociativeContainer(s, hash);
} }
template <class Key, class T> template <class Key, class T>
inline QDataStream &operator<<(QDataStream &s, const QHash<Key, T> &hash) inline QDataStreamIfHasOStreamOperators<Key, T> operator<<(QDataStream &s, const QHash<Key, T> &hash)
{ {
return QtPrivate::writeAssociativeContainer(s, hash); return QtPrivate::writeAssociativeContainer(s, hash);
} }
template <class Key, class T> template <class Key, class T>
inline QDataStream &operator>>(QDataStream &s, QMultiHash<Key, T> &hash) inline QDataStreamIfHasIStreamOperators<Key, T> operator>>(QDataStream &s, QMultiHash<Key, T> &hash)
{ {
return QtPrivate::readAssociativeContainer(s, hash); return QtPrivate::readAssociativeContainer(s, hash);
} }
template <class Key, class T> template <class Key, class T>
inline QDataStream &operator<<(QDataStream &s, const QMultiHash<Key, T> &hash) inline QDataStreamIfHasOStreamOperators<Key, T> operator<<(QDataStream &s, const QMultiHash<Key, T> &hash)
{ {
return QtPrivate::writeAssociativeMultiContainer(s, hash); return QtPrivate::writeAssociativeMultiContainer(s, hash);
} }
template <class Key, class T> template <class Key, class T>
inline QDataStream &operator>>(QDataStream &s, QMap<Key, T> &map) inline QDataStreamIfHasIStreamOperators<Key, T> operator>>(QDataStream &s, QMap<Key, T> &map)
{ {
return QtPrivate::readAssociativeContainer(s, map); return QtPrivate::readAssociativeContainer(s, map);
} }
template <class Key, class T> template <class Key, class T>
inline QDataStream &operator<<(QDataStream &s, const QMap<Key, T> &map) inline QDataStreamIfHasOStreamOperators<Key, T> operator<<(QDataStream &s, const QMap<Key, T> &map)
{ {
return QtPrivate::writeAssociativeContainer(s, map); return QtPrivate::writeAssociativeContainer(s, map);
} }
template <class Key, class T> template <class Key, class T>
inline QDataStream &operator>>(QDataStream &s, QMultiMap<Key, T> &map) inline QDataStreamIfHasIStreamOperators<Key, T> operator>>(QDataStream &s, QMultiMap<Key, T> &map)
{ {
return QtPrivate::readAssociativeContainer(s, map); return QtPrivate::readAssociativeContainer(s, map);
} }
template <class Key, class T> template <class Key, class T>
inline QDataStream &operator<<(QDataStream &s, const QMultiMap<Key, T> &map) inline QDataStreamIfHasOStreamOperators<Key, T> operator<<(QDataStream &s, const QMultiMap<Key, T> &map)
{ {
return QtPrivate::writeAssociativeMultiContainer(s, map); return QtPrivate::writeAssociativeMultiContainer(s, map);
} }
#ifndef QT_NO_DATASTREAM #ifndef QT_NO_DATASTREAM
template <class T1, class T2> template <class T1, class T2>
inline QDataStream& operator>>(QDataStream& s, std::pair<T1, T2> &p) inline QDataStreamIfHasIStreamOperators<T1, T2> operator>>(QDataStream& s, std::pair<T1, T2> &p)
{ {
s >> p.first >> p.second; s >> p.first >> p.second;
return s; return s;
} }
template <class T1, class T2> template <class T1, class T2>
inline QDataStream& operator<<(QDataStream& s, const std::pair<T1, T2> &p) inline QDataStreamIfHasOStreamOperators<T1, T2> operator<<(QDataStream& s, const std::pair<T1, T2> &p)
{ {
s << p.first << p.second; s << p.first << p.second;
return s; return s;

10
tests/auto/corelib/io/qdebug/tst_qdebug.cpp
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@ -35,11 +35,13 @@
#include <QtConcurrentRun> #include <QtConcurrentRun>
#include <QFutureSynchronizer> #include <QFutureSynchronizer>
static_assert(QTypeTraits::has_ostream_v<QDebug, int>); static_assert(QTypeTraits::has_ostream_operator_v<QDebug, int>);
static_assert(QTypeTraits::has_ostream_v<QDebug, QList<int>>); static_assert(QTypeTraits::has_ostream_operator_v<QDebug, QList<int>>);
static_assert(QTypeTraits::has_ostream_operator_v<QDebug, QMap<int, QString>>);
struct NonStreamable {}; struct NonStreamable {};
static_assert(!QTypeTraits::has_ostream_v<QDebug, NonStreamable>); static_assert(!QTypeTraits::has_ostream_operator_v<QDebug, NonStreamable>);
static_assert(!QTypeTraits::has_ostream_v<QDebug, QList<NonStreamable>>); static_assert(!QTypeTraits::has_ostream_operator_v<QDebug, QList<NonStreamable>>);
static_assert(!QTypeTraits::has_ostream_operator_v<QDebug, QMap<int, NonStreamable>>);
class tst_QDebug: public QObject class tst_QDebug: public QObject
{ {

8
tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp
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@ -36,6 +36,14 @@
#include <QtGui/QPixmap> #include <QtGui/QPixmap>
#include <QtGui/QTextLength> #include <QtGui/QTextLength>
static_assert(QTypeTraits::has_ostream_operator_v<QDataStream, int>);
static_assert(QTypeTraits::has_ostream_operator_v<QDataStream, QList<int>>);
static_assert(QTypeTraits::has_ostream_operator_v<QDataStream, QMap<int, QString>>);
struct NonStreamable {};
static_assert(!QTypeTraits::has_ostream_operator_v<QDataStream, NonStreamable>);
static_assert(!QTypeTraits::has_ostream_operator_v<QDataStream, QList<NonStreamable>>);
static_assert(!QTypeTraits::has_ostream_operator_v<QDataStream, QMap<int, NonStreamable>>);
class tst_QDataStream : public QObject class tst_QDataStream : public QObject
{ {
Q_OBJECT Q_OBJECT