diff options
| -rw-r--r-- | src/corelib/doc/snippets/qstring/stringbuilder.cpp | 23 | ||||
| -rw-r--r-- | src/corelib/text/qstring.cpp | 21 | ||||
| -rw-r--r-- | src/corelib/text/qstringbuilder.cpp | 47 |
3 files changed, 71 insertions, 20 deletions
diff --git a/src/corelib/doc/snippets/qstring/stringbuilder.cpp b/src/corelib/doc/snippets/qstring/stringbuilder.cpp index 6b3175d48a..61b7a9a133 100644 --- a/src/corelib/doc/snippets/qstring/stringbuilder.cpp +++ b/src/corelib/doc/snippets/qstring/stringbuilder.cpp @@ -1,6 +1,8 @@ // Copyright (C) 2016 The Qt Company Ltd. // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause +#include <QString> + using namespace Qt::StringLiterals; //! [0] @@ -25,3 +27,24 @@ using namespace Qt::StringLiterals; QLatin1StringView world("world"); QString message = hello % el % world % QChar('!'); //! [5] + +//! [6] + QString str("QStringBuilder"); + + // "s" type is deduced as QStringBuilder + auto s = "Like hot glue, " % str % " concatenates strings"; + + // Similarly the return type of this lambda is deduced as QStringBuilder + auto concatenateStr = []() { + return "Like hot glue, " % str % " concatenates strings"; + }; +//! [6] + +//! [7] + QString s = "Like hot glue, " % str % " concatenates strings"; + + // With a lambda, specify a trailing return type + auto concatenateStr = []() -> QString { + return "Like hot glue, " % str % " concatenates strings"; + }; +//! [7] diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp index 8927bbeb57..a08cf3f9ca 100644 --- a/src/corelib/text/qstring.cpp +++ b/src/corelib/text/qstring.cpp @@ -2039,7 +2039,7 @@ void qtWarnAboutInvalidRegularExpression(const QString &pattern, const char *whe Many strings are known at compile time. But the trivial constructor QString("Hello"), will copy the contents of the string, - treating the contents as Latin-1. To avoid this one can use the + treating the contents as Latin-1. To avoid this, one can use the QStringLiteral macro to directly create the required data at compile time. Constructing a QString out of the literal does then not cause any overhead at runtime. @@ -2093,14 +2093,21 @@ void qtWarnAboutInvalidRegularExpression(const QString &pattern, const char *whe \snippet qstring/stringbuilder.cpp 5 - A more global approach which is the most convenient but - not entirely source compatible, is to this define in your - .pro file: + A more global approach, which is more convenient but not entirely source + compatible, is to define \c QT_USE_QSTRINGBUILDER (by adding it to the compiler + flags) at build time. This will make concatenating strings with \c{'+'} work the + same way as \c{QStringBuilder} \c{'%'}. - \snippet qstring/stringbuilder.cpp 3 + \note Take care when using the \c auto keyword with the result of + string concatenation using QStringBuilder: + \snippet qstring/stringbuilder.cpp 6 - and the \c{'+'} will automatically be performed as the - \c{QStringBuilder} \c{'%'} everywhere. + Typically this is not what is expected (and can result in undefined behavior). + This issue can be fixed by specifying the return type: + \snippet qstring/stringbuilder.cpp 7 + + \note \l {https://invent.kde.org/sdk/clazy} {Clazy} has a check, auto-unexpected-qstringbuilder, + that catches this issue. \section1 Maximum Size and Out-of-memory Conditions diff --git a/src/corelib/text/qstringbuilder.cpp b/src/corelib/text/qstringbuilder.cpp index d4ab8db0b2..47da2e5051 100644 --- a/src/corelib/text/qstringbuilder.cpp +++ b/src/corelib/text/qstringbuilder.cpp @@ -57,36 +57,57 @@ QT_BEGIN_NAMESPACE if there are three or more of them, and performs equally well in other cases. + \note Definnig \c QT_USE_STRINGBUILDER at build time (this is the default + when building Qt libraries and tools), will make using \c {'+'} when + concatenating strings work the same way as \c operator%(). + \sa QLatin1StringView, QString */ -/*! \fn template <typename A, typename B> QStringBuilder<A, B>::QStringBuilder(const A &a, const B &b) - Constructs a QStringBuilder from \a a and \a b. +/*! + \internal + \fn template <typename A, typename B> QStringBuilder<A, B>::QStringBuilder(const A &a, const B &b) + + Constructs a QStringBuilder from \a a and \a b. */ -/* \fn template <typename A, typename B> QStringBuilder<A, B>::operator%(const A &a, const B &b) +/*! + \internal + \fn template <typename A, typename B> QStringBuilder<A, B>::operator%(const A &a, const B &b) Returns a \c QStringBuilder object that is converted to a QString object when assigned to a variable of QString type or passed to a function that takes a QString parameter. - This function is usable with arguments of type \c QString, - \c QLatin1StringView, - \c QChar, \c QLatin1Char, and \c char. + This function is usable with arguments of any of the following types: + \list + \li \c QAnyStringView, + \li \c QString, \c QStringView + \li \c QByteArray, \c QByteArrayView, \c QLatin1StringView + \li \c QChar, \c QLatin1Char, \c char, (since 5.10:) \c char16_t + \li (since 5.10:) \c{const char16_t[]} (\c{u"foo"}), + \endlist */ -/* \fn template <typename A, typename B> QByteArray QStringBuilder<A, B>::toLatin1() const - Returns a Latin-1 representation of the string as a QByteArray. The - returned byte array is undefined if the string contains non-Latin1 - characters. - */ -/* \fn template <typename A, typename B> QByteArray QStringBuilder<A, B>::toUtf8() const - Returns a UTF-8 representation of the string as a QByteArray. +/*! + \internal + \fn template <typename A, typename B> QByteArray QStringBuilder<A, B>::toLatin1() const + + Returns a Latin-1 representation of the string as a QByteArray. It + is undefined behavior if the string contains non-Latin1 characters. */ +/*! + \internal + \fn template <typename A, typename B> QByteArray QStringBuilder<A, B>::toUtf8() const + + Returns a UTF-8 representation of the string as a QByteArray. + */ /*! \internal + Converts the UTF-8 string viewed by \a in to UTF-16 and writes the result + to the buffer starting at \a out. */ void QAbstractConcatenable::convertFromUtf8(QByteArrayView in, QChar *&out) noexcept { |