Support logging direct to journald, if enabled.

Instead of merely intercepting logging output from stdout/stderr from the
journal side of started processes, this has the advantage of meaning that the
origin process name will be correct.

fprintf won't work, because if a process starts children (like e.g. a
homescreen does), then their stdout/stderr are merged into their parent, and
journal has no way of differentiating the origin.

We are also able to store information about the context of logging, which might
be useful in post-mortem cases.

[ChangeLog][Platform Specific Changes][Linux] Systems with systemd may now pass
-journald to configure to send logging output to journald. Logging will still be
sent to stderr for interactive applications (run from a tty) or with
QT_NO_JOURNALD_LOG set to a non-empty value.

Change-Id: Ib260cec1ea87390bf44f267d217d795583407d00
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

config.tests/unix/journald/journald.c

@@ -0,0 +1,48 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Jolla Ltd, author: <robin.burchell@jollamobile.com>
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the config.tests of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <systemd/sd-journal.h>
+
+int main(int argc, char **argv)
+{
+    sd_journal_print_with_location(LOG_INFO, "CODE_FILE=foo.c", "CODE_LINE=0", "unknown_function", "test message");
+    return 0;
+}

config.tests/unix/journald/journald.pro

@@ -0,0 +1,6 @@
+SOURCES = journald.c
+
+CONFIG += link_pkgconfig
+PKGCONFIG_PRIVATE += libsystemd-journal
+
+CONFIG -= qt

configure

@@ -596,6 +596,7 @@ CFG_XINERAMA=runtime
 CFG_XFIXES=runtime
 CFG_ZLIB=auto
 CFG_MTDEV=auto
+CFG_JOURNALD=no
 CFG_SQLITE=qt
 CFG_GIF=auto
 CFG_PNG=yes
@@ -1590,6 +1591,13 @@ while [ "$#" -gt 0 ]; do
             UNKNOWN_OPT=yes
         fi
         ;;
+    journald)
+        if [ "$VAL" = "yes" ] || [ "$VAL" = "no" ]; then
+            CFG_JOURNALD="$VAL"
+        else
+            UNKNOWN_OPT=yes
+        fi
+        ;;
     sqlite)
         if [ "$VAL" = "system" ]; then
             CFG_SQLITE=system
@@ -2307,6 +2315,9 @@ Third Party Libraries:
     -no-mtdev .........  Do not compile mtdev support.
  +  -mtdev ............. Enable mtdev support.
 
+ +  -no-journald ....... Do not send logging output to journald.
+    -journald .......... Send logging output to journald.
+
     -no-gif ............ Do not compile GIF reading support.
 
     -no-libpng ......... Do not compile PNG support.
@@ -4416,6 +4427,23 @@ if [ "$CFG_MTDEV" = "no" ]; then
     QMakeVar add DEFINES QT_NO_MTDEV
 fi
 
+if [ "$CFG_JOURNALD" != "no" ]; then
+    if compileTest unix/journald "journald"; then
+        CFG_JOURNALD=yes
+        QMAKE_CONFIG="$QMAKE_CONFIG journald"
+    else
+        if [ "$CFG_JOURNALD" != "auto" ] && [ "$CFG_CONFIGURE_EXIT_ON_ERROR" = "yes" ]; then
+            echo "journald support cannot be enabled due to functionality tests!"
+            echo " Turn on verbose messaging (-v) to $0 to see the final report."
+            echo " If you believe this message is in error you may use the continue"
+            echo " switch (-continue) to $0 to continue."
+            exit 101
+        else
+            CFG_JOURNALD=no
+        fi
+    fi
+fi
+
 if [ "$CFG_LARGEFILE" = "auto" ]; then
     #Large files should be enabled for all Linux systems
     CFG_LARGEFILE=yes
@@ -6724,6 +6752,7 @@ report_support_plugin "    JPEG ................." "$CFG_JPEG" "$CFG_LIBJPEG" Qt
 report_support_plugin "    PNG .................." "$CFG_PNG" "$CFG_LIBPNG" QtGui
 report_support "  Glib ..................." "$CFG_GLIB"
 report_support "  GTK theme .............." "$CFG_QGTKSTYLE"
+report_support "  journald ..............." "$CFG_JOURNALD"
 report_support "  Large File ............." "$CFG_LARGEFILE"
 report_support "  mtdev .................." "$CFG_MTDEV" yes "system library"
 report_support "  Networking:"

src/corelib/global/global.pri

@@ -51,3 +51,9 @@ slog2 {
     LIBS_PRIVATE += -lslog2
     DEFINES += QT_USE_SLOG2
 }
+
+journald {
+    CONFIG += link_pkgconfig
+    PKGCONFIG_PRIVATE += libsystemd-journal
+    DEFINES += QT_USE_JOURNALD
+}

src/corelib/global/qlogging.cpp

@@ -63,6 +63,11 @@
 #include <android/log.h>
 #endif
 
+#if defined(QT_USE_JOURNALD) && !defined(QT_BOOTSTRAPPED)
+# include <systemd/sd-journal.h>
+# include <unistd.h>
+#endif
+
 #include <stdio.h>
 
 QT_BEGIN_NAMESPACE
@@ -866,6 +871,37 @@ Q_CORE_EXPORT QtMsgHandler qInstallMsgHandler(QtMsgHandler);
 static QtMsgHandler msgHandler = 0;                // pointer to debug handler (without context)
 static QtMessageHandler messageHandler = 0;         // pointer to debug handler (with context)
 
+#if defined(QT_USE_JOURNALD) && !defined(QT_BOOTSTRAPPED)
+static void systemd_default_message_handler(QtMsgType type,
+                                            const QMessageLogContext &context,
+                                            const QString &message)
+{
+    int priority = LOG_INFO; // Informational
+    switch (type) {
+    case QtDebugMsg:
+        priority = LOG_DEBUG; // Debug-level messages
+        break;
+    case QtWarningMsg:
+        priority = LOG_WARNING; // Warning conditions
+        break;
+    case QtCriticalMsg:
+        priority = LOG_CRIT; // Critical conditions
+        break;
+    case QtFatalMsg:
+        priority = LOG_ALERT; // Action must be taken immediately
+        break;
+    }
+
+    char filebuf[PATH_MAX + sizeof("CODE_FILE=")];
+    snprintf(filebuf, sizeof(filebuf), "CODE_FILE=%s", context.file ? context.file : "unknown");
+
+    char linebuf[20];
+    snprintf(linebuf, sizeof(linebuf), "CODE_LINE=%d", context.line);
+
+    sd_journal_print_with_location(priority, filebuf, linebuf, context.function ? context.function : "unknown", "%s", message.toUtf8().constData());
+}
+#endif
+
 #ifdef Q_OS_ANDROID
 static void android_default_message_handler(QtMsgType type,
                                   const QMessageLogContext &context,
@@ -902,6 +938,18 @@ static void qDefaultMessageHandler(QtMsgType type, const QMessageLogContext &con
 
 #if defined(QT_USE_SLOG2)
     slog2_default_handler(type, logMessage.toLocal8Bit().constData());
+#elif defined(QT_USE_JOURNALD) && !defined(QT_BOOTSTRAPPED)
+    // We use isatty to catch the obvious case of someone running something interactively.
+    // We also support an environment variable for Qt Creator use, or more complicated cases like subprocesses.
+    static bool logToConsole = isatty(fileno(stdin)) || !qEnvironmentVariableIsEmpty("QT_NO_JOURNALD_LOG");
+    if (Q_LIKELY(!logToConsole)) {
+        // remove trailing \n, systemd appears to want them newline-less
+        logMessage.chop(1);
+        systemd_default_message_handler(type, context, logMessage);
+    } else {
+        fprintf(stderr, "%s", logMessage.toUtf8().constData());
+        fflush(stderr);
+    }
 #elif defined(Q_OS_ANDROID)
     static bool logToAndroid = qEnvironmentVariableIsEmpty("QT_ANDROID_PLAIN_LOG");
     if (logToAndroid) {