QT_USE_QSTRINGBUILDER to fix source compatibility

In 4.8 we added support for using StringBuilder with QByteArray.
But this is breaking source compatibility for people that used
QT_USE_FAST_OPERATOR_PLUS in Qt 4.7. So we introduce a new macro

Notice that QT_USE_FAST_CONCATENATION was not working without
QT_USE_FAST_OPERATOR_PLUS, so we remove the checking of that macro.

Reviewed-by: joao
(cherry picked from commit 8447f5616be731d78081f326bb9cb3f5aa9087a4)

4 files changed, 15 insertions, 20 deletions

diff --git a/src/corelib/tools/qbytearray.h b/src/corelib/tools/qbytearray.h
index 0627b4e568..df58d95131 100644
--- a/src/corelib/tools/qbytearray.h
+++ b/src/corelib/tools/qbytearray.h
@@ -57,9 +57,10 @@
 #  ifdef QT_USE_FAST_OPERATOR_PLUS
 #    undef QT_USE_FAST_OPERATOR_PLUS
 #  endif
-#  ifdef QT_USE_FAST_CONCATENATION
-#    undef QT_USE_FAST_CONCATENATION
+#  ifdef QT_USE_QSTRINGBUILDER
+#    undef QT_USE_QSTRINGBUILDER
 #  endif
+
 #endif
 
 
@@ -559,8 +560,7 @@ inline bool operator>=(const QByteArray &a1, const char *a2)
 { return qstrcmp(a1, a2) >= 0; }
 inline bool operator>=(const char *a1, const QByteArray &a2)
 { return qstrcmp(a1, a2) >= 0; }
-#ifndef QT_USE_FAST_OPERATOR_PLUS
-# ifndef QT_USE_FAST_CONCATENATION
+#if !defined(QT_USE_QSTRINGBUILDER)
 inline const QByteArray operator+(const QByteArray &a1, const QByteArray &a2)
 { return QByteArray(a1) += a2; }
 inline const QByteArray operator+(const QByteArray &a1, const char *a2)
@@ -571,8 +571,7 @@ inline const QByteArray operator+(const char *a1, const QByteArray &a2)
 { return QByteArray(a1) += a2; }
 inline const QByteArray operator+(char a1, const QByteArray &a2)
 { return QByteArray(&a1, 1) += a2; }
-# endif // QT_USE_FAST_CONCATENATION
-#endif // QT_USE_FAST_OPERATOR_PLUS
+#endif // QT_USE_QSTRINGBUILDER
 inline QBool QByteArray::contains(const char *c) const
 { return QBool(indexOf(c) != -1); }
 inline QByteArray &QByteArray::replace(char before, const char *c)
@@ -615,7 +614,7 @@ QT_END_NAMESPACE
 
 QT_END_HEADER
 
-#ifdef QT_USE_FAST_CONCATENATION
+#ifdef QT_USE_QSTRINGBUILDER
 #include <QtCore/qstring.h>
 #endif
 
diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index 5493ba915b..3b3f715b9d 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -777,16 +777,12 @@ const QString::Null QString::null = { };
 
     \snippet doc/src/snippets/qstring/stringbuilder.cpp 5
 
-    A more global approach is to include this define:
+    A more global approach which is the most convenient but
+    not entirely source compatible, is to this define in your
+    .pro file:
 
     \snippet doc/src/snippets/qstring/stringbuilder.cpp 3
 
-    and use \c{'%'} instead of \c{'+'} for string concatenation
-    everywhere. The third approach, which is the most convenient but
-    not entirely source compatible, is to include two defines:
-
-    \snippet doc/src/snippets/qstring/stringbuilder.cpp 4
-
     and the \c{'+'} will automatically be performed as the
     \c{QStringBuilder} \c{'%'} everywhere.
 
diff --git a/src/corelib/tools/qstring.h b/src/corelib/tools/qstring.h
index 6418a8cbd4..7c4367efde 100644
--- a/src/corelib/tools/qstring.h
+++ b/src/corelib/tools/qstring.h
@@ -1016,8 +1016,7 @@ inline int QByteArray::findRev(const QString &s, int from) const
 #  endif // QT3_SUPPORT
 #endif // QT_NO_CAST_TO_ASCII
 
-#ifndef QT_USE_FAST_OPERATOR_PLUS
-# ifndef QT_USE_FAST_CONCATENATION
+#if !defined(QT_USE_FAST_OPERATOR_PLUS) && !defined(QT_USE_QSTRINGBUILDER)
 inline const QString operator+(const QString &s1, const QString &s2)
 { QString t(s1); t += s2; return t; }
 inline const QString operator+(const QString &s1, QChar s2)
@@ -1038,8 +1037,7 @@ inline QT_ASCII_CAST_WARN const QString operator+(const QByteArray &ba, const QS
 inline QT_ASCII_CAST_WARN const QString operator+(const QString &s, const QByteArray &ba)
 { QString t(s); t += QString::fromAscii(ba.constData(), qstrnlen(ba.constData(), ba.size())); return t; }
 #  endif // QT_NO_CAST_FROM_ASCII
-# endif // QT_USE_FAST_CONCATENATION
-#endif // QT_USE_FAST_OPERATOR_PLUS
+#endif // QT_USE_QSTRINGBUILDER
 
 #ifndef QT_NO_STL
 inline std::string QString::toStdString() const
@@ -1288,7 +1286,7 @@ QT_END_NAMESPACE
 
 QT_END_HEADER
 
-#ifdef QT_USE_FAST_CONCATENATION
+#if defined(QT_USE_FAST_OPERATOR_PLUS) || defined(QT_USE_QSTRINGBUILDER)
 #include <QtCore/qstringbuilder.h>
 #endif
 
diff --git a/src/corelib/tools/qstringbuilder.h b/src/corelib/tools/qstringbuilder.h
index 2d3475fed9..029aa0b216 100644
--- a/src/corelib/tools/qstringbuilder.h
+++ b/src/corelib/tools/qstringbuilder.h
@@ -410,7 +410,9 @@ operator%(const A &a, const B &b)
    return QStringBuilder<typename QConcatenable<A>::type, typename QConcatenable<B>::type>(a, b);
 }
 
-#ifdef QT_USE_FAST_OPERATOR_PLUS
+// QT_USE_FAST_OPERATOR_PLUS was introduced in 4.7, QT_USE_QSTRINGBUILDER is to be used from 4.8 onwards
+// QT_USE_FAST_OPERATOR_PLUS does not remove the normal operator+ for QByteArray
+#if defined(QT_USE_FAST_OPERATOR_PLUS) || defined(QT_USE_QSTRINGBUILDER)
 template <typename A, typename B>
 QStringBuilder<typename QConcatenable<A>::type, typename QConcatenable<B>::type>
 operator+(const A &a, const B &b)