From 8e98a161e993c6636d217276a0f2373d642ff050 Mon Sep 17 00:00:00 2001 From: Giuseppe D'Angelo Date: Sat, 15 Feb 2020 00:11:22 +0100 Subject: 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 ( 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 --- src/corelib/serialization/qdatastream.cpp | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'src/corelib/serialization/qdatastream.cpp') diff --git a/src/corelib/serialization/qdatastream.cpp b/src/corelib/serialization/qdatastream.cpp index 3026e554bf..316a164c6d 100644 --- a/src/corelib/serialization/qdatastream.cpp +++ b/src/corelib/serialization/qdatastream.cpp @@ -1119,6 +1119,16 @@ int QDataStream::readRawData(char *s, int len) return readBlock(s, len); } +/*! \fn template QDataStream &operator>>(QDataStream &in, std::pair &pair) + \since 6.0 + \relates QDataStream + + Reads a pair from stream \a in into \a pair. + + This function requires the T1 and T2 types to implement \c operator>>(). + + \sa {Serializing Qt Data Types} +*/ /***************************************************************************** QDataStream write functions @@ -1446,6 +1456,18 @@ int QDataStream::skipRawData(int len) return skipResult; } +/*! + \fn template QDataStream &operator<<(QDataStream &out, const std::pair &pair) + \since 6.0 + \relates QDataStream + + Writes the pair \a pair to stream \a out. + + This function requires the T1 and T2 types to implement \c operator<<(). + + \sa {Serializing Qt Data Types} +*/ + QT_END_NAMESPACE #endif // QT_NO_DATASTREAM -- cgit v1.2.3