Introduce qUtf8Printable() macro to qglobal.h

This macro is equivalent to arg.toUtf8().constData().
It is usable for "%s" arguments of qDebug(), qWarning(), qFatal(),
qCritical().

Change-Id: I2d9956e6651271e1e2183dce9c835511cf923bf3
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

4 files changed, 93 insertions, 11 deletions

diff --git a/src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp b/src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp
index b907c9acb1..5befebc982 100644
--- a/src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp
+++ b/src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp
@@ -305,7 +305,7 @@ void load(const QString &fileName)
 {
     QFile file(fileName);
     if (!file.exists())
-        qCritical("File '%s' does not exist!", qPrintable(fileName));
+        qCritical("File '%s' does not exist!", qUtf8Printable(fileName));
 }
 //! [28]
 
@@ -424,7 +424,7 @@ void TheClass::addLabels()
 
 
 //! [37]
-qWarning("%s: %s", qPrintable(key), qPrintable(value));
+qWarning("%s: %s", qUtf8Printable(key), qUtf8Printable(value));
 //! [37]
 
 
diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index fb95a1966f..98460481ca 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -580,8 +580,8 @@ Q_STATIC_ASSERT_X(UCHAR_MAX == 255, "Qt assumes that char is 8 bits");
     64-bit integer literals in a platform-independent way. The
     Q_CHECK_PTR() macro prints a warning containing the source code's
     file name and line number, saying that the program ran out of
-    memory, if the pointer is 0. The qPrintable() macro represent an
-    easy way of printing text.
+    memory, if the pointer is 0. The qPrintable() and qUtf8Printable()
+    macros represent an easy way of printing text.
 
     Finally, the QT_POINTER_SIZE macro expands to the size of a
     pointer in bytes, and the QT_VERSION and QT_VERSION_STR macros
@@ -3356,17 +3356,31 @@ int qrand()
     qPrintable() is used. This is because the array returned by
     QString::toLocal8Bit() will fall out of scope.
 
+    \note qDebug(), qWarning(), qCritical(), qFatal() expect %s
+    arguments to be UTF-8 encoded, while qPrintable() converts to
+    local 8-bit encoding. Therefore qUtf8Printable() should be used
+    for logging strings instead of qPrintable().
+
+    \sa qUtf8Printable()
+*/
+
+/*!
+    \macro const char *qUtf8Printable(const QString &str)
+    \relates <QtGlobal>
+    \since 5.4
+
+    Returns \a str as a \c{const char *}. This is equivalent to
+    \a{str}.toUtf8().constData().
+
+    The char pointer will be invalid after the statement in which
+    qUtf8Printable() is used. This is because the array returned by
+    QString::toUtf8() will fall out of scope.
+
     Example:
 
     \snippet code/src_corelib_global_qglobal.cpp 37
 
-    \note qDebug(), qWarning(), qCritical(), qFatal() expect %s
-    arguments to be UTF-8 encoded, while qPrintable() converts to
-    local 8-bit encoding. Therefore using qPrintable for logging
-    strings is only safe if the argument contains only ASCII
-    characters.
-
-    \sa qDebug(), qWarning(), qCritical(), qFatal()
+    \sa qPrintable(), qDebug(), qWarning(), qCritical(), qFatal()
 */
 
 /*!
diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index a9621e744c..80c9992e25 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -645,6 +645,10 @@ inline void qUnused(T &x) { (void)x; }
 #  define qPrintable(string) QString(string).toLocal8Bit().constData()
 #endif
 
+#ifndef qUtf8Printable
+#  define qUtf8Printable(string) QString(string).toUtf8().constData()
+#endif
+
 class QString;
 Q_CORE_EXPORT QString qt_error_string(int errorCode = -1);
 
diff --git a/tests/auto/corelib/global/qglobal/tst_qglobal.cpp b/tests/auto/corelib/global/qglobal/tst_qglobal.cpp
index 4eb3e4fc98..0389ae7976 100644
--- a/tests/auto/corelib/global/qglobal/tst_qglobal.cpp
+++ b/tests/auto/corelib/global/qglobal/tst_qglobal.cpp
@@ -43,6 +43,9 @@
 #include <QtTest/QtTest>
 #include <QtCore/qtypetraits.h>
 
+#include <QPair>
+#include <QTextCodec>
+
 class tst_QGlobal: public QObject
 {
     Q_OBJECT
@@ -60,6 +63,8 @@ private slots:
     void isEnum();
     void qAlignOf();
     void integerForSize();
+    void qprintable();
+    void qprintable_data();
 };
 
 void tst_QGlobal::qIsNull()
@@ -588,5 +593,64 @@ void tst_QGlobal::integerForSize()
     Q_STATIC_ASSERT(sizeof(QIntegerForSize<8>::Unsigned) == 8);
 }
 
+typedef QPair<const char *, const char *> stringpair;
+Q_DECLARE_METATYPE(stringpair)
+
+void tst_QGlobal::qprintable()
+{
+    QFETCH(QList<stringpair>, localestrings);
+    QFETCH(int, utf8index);
+
+    QVERIFY(utf8index >= 0 && utf8index < localestrings.count());
+    if (utf8index < 0 || utf8index >= localestrings.count())
+        return;
+
+    const char *const utf8string = localestrings.at(utf8index).second;
+
+    QString string = QString::fromUtf8(utf8string);
+
+    foreach (const stringpair &pair, localestrings) {
+        QTextCodec *codec = QTextCodec::codecForName(pair.first);
+        if (!codec)
+            continue;
+        QTextCodec::setCodecForLocale(codec);
+        // test qPrintable()
+        QVERIFY(qstrcmp(qPrintable(string), pair.second) == 0);
+        foreach (const stringpair &pair2, localestrings) {
+            if (pair2.second == pair.second)
+                continue;
+            QVERIFY(qstrcmp(qPrintable(string), pair2.second) != 0);
+        }
+        // test qUtf8Printable()
+        QVERIFY(qstrcmp(qUtf8Printable(string), utf8string) == 0);
+        foreach (const stringpair &pair2, localestrings) {
+            if (qstrcmp(pair2.second, utf8string) == 0)
+                continue;
+            QVERIFY(qstrcmp(qUtf8Printable(string), pair2.second) != 0);
+        }
+    }
+
+    QTextCodec::setCodecForLocale(0);
+}
+
+void tst_QGlobal::qprintable_data()
+{
+    QTest::addColumn<QList<stringpair> >("localestrings");
+    QTest::addColumn<int>("utf8index"); // index of utf8 string
+
+    // Unicode: HIRAGANA LETTER A, I, U, E, O (U+3442, U+3444, U+3446, U+3448, U+344a)
+    static const char *const utf8string = "\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88\xe3\x81\x8a";
+    static const char *const eucjpstring = "\xa4\xa2\xa4\xa4\xa4\xa6\xa4\xa8\xa4\xaa";
+    static const char *const sjisstring = "\x82\xa0\x82\xa2\x82\xa4\x82\xa6\x82\xa8";
+
+    QList<stringpair> japanesestrings;
+    japanesestrings << stringpair("UTF-8", utf8string)
+                    << stringpair("EUC-JP", eucjpstring)
+                    << stringpair("Shift_JIS", sjisstring);
+
+    QTest::newRow("Japanese") << japanesestrings << 0;
+
+}
+
 QTEST_APPLESS_MAIN(tst_QGlobal)
 #include "tst_qglobal.moc"