Debugger: Enable attaching with -client option.

Make it possible to trigger a debug-attach in a running instance
of Qt Creator by means of -client, use that in qtcdebugger, thus
enabling it to attaching to crashing executables in run mode
(Windows/CDB).

Modify IPlugin and application so that the complete command line is
serialized and transmitted to a running instance via QtSingleApplication
if -client is specified. Introduce IPlugin::remoteArgument and use that
in core for opening files and in the debugger for attaching.

Use -client in qtcdebugger with some logic to keep it alive as long as
the debuggee, make CDB break in that case as the events are not replayed
correctly in case the debugger is not spawned by the registered handler.
Rubber-stamped-by: con <qtc-committer@nokia.com>

src/tools/qtcdebugger/main.cpp

@@ -41,6 +41,7 @@
 #include <QtCore/QByteArray>
 #include <QtCore/QString>
 #include <QtCore/QDir>
+#include <QtCore/QTime>
 #include <QtCore/QProcess>
 #include <QtGui/QPushButton>
 
@@ -61,6 +62,7 @@ static const WCHAR *debuggerRegistryValueNameC = L"Debugger";
 static const WCHAR *debuggerRegistryDefaultValueNameC = L"Debugger.Default";
 
 static const char *linkC = "http://msdn.microsoft.com/en-us/library/cc266343.aspx";
+static const char *creatorBinaryC = "qtcreator.exe";
 
 static inline QString wCharToQString(const WCHAR *w) { return QString::fromUtf16(reinterpret_cast<const ushort *>(w)); }
 #ifdef __GNUC__
@@ -343,23 +345,49 @@ static QString getProcessBaseName(DWORD pid)
 
 // ------- main modes
 
-bool startCreatorAsDebugger(QString *errorMessage)
+static bool waitForProcess(DWORD pid)
+{
+    HANDLE handle = OpenProcess(PROCESS_QUERY_INFORMATION|READ_CONTROL|SYNCHRONIZE, false, pid);
+    if (handle == NULL)
+        return false;
+    const DWORD waitResult = WaitForSingleObject(handle, INFINITE);
+    CloseHandle(handle);
+    return waitResult == WAIT_OBJECT_0;
+}
+
+bool startCreatorAsDebugger(bool asClient, QString *errorMessage)
 {
     const QString dir = QApplication::applicationDirPath();
-    const QString binary = dir + QLatin1String("/qtcreator.exe");
+    const QString binary = dir + QLatin1Char('/') + QLatin1String(creatorBinaryC);
     QStringList args;
+    if (asClient)
+        args << QLatin1String("-client");
     args << QLatin1String("-debug") << QString::number(argProcessId)
             << QLatin1String("-wincrashevent") << QString::number(argWinCrashEvent);
     if (debug)
         qDebug() << binary << args;
     QProcess p;
     p.setWorkingDirectory(dir);
+    QTime executionTime;
+    executionTime.start();
     p.start(binary, args, QIODevice::NotOpen);
     if (!p.waitForStarted()) {
         *errorMessage = QString::fromLatin1("Unable to start %1!").arg(binary);
         return false;
     }
-    p.waitForFinished(-1);
+    // Short execution time: indicates that -client was passed on attach to
+    // another running instance of Qt Creator. Keep alive as long as user
+    // does not close the process. If that fails, try to launch 2nd instance.
+    const bool waitResult = p.waitForFinished(-1);
+    const bool ranAsClient = asClient && (executionTime.elapsed() < 10000);
+    if (waitResult && p.exitStatus() == QProcess::NormalExit && ranAsClient) {
+        if (p.exitCode() == 0) {
+            waitForProcess(argProcessId);
+        } else {
+            errorMessage->clear();
+            return startCreatorAsDebugger(false, errorMessage);
+        }
+    }
     return true;
 }
 
@@ -408,7 +436,8 @@ bool startDefaultDebugger(QString *errorMessage)
 bool chooseDebugger(QString *errorMessage)
 {
     QString defaultDebugger;
-    const QString msg = QString::fromLatin1("The application \"%1\" (process id %2)  crashed. Would you like to debug it?").arg(getProcessBaseName(argProcessId)).arg(argProcessId);
+    const QString processName = getProcessBaseName(argProcessId);
+    const QString msg = QString::fromLatin1("The application \"%1\" (process id %2)  crashed. Would you like to debug it?").arg(processName).arg(argProcessId);
     QMessageBox msgBox(QMessageBox::Information, QLatin1String(titleC), msg, QMessageBox::Cancel);
     QPushButton *creatorButton = msgBox.addButton(QLatin1String("Debug with Qt Creator"), QMessageBox::AcceptRole);
     QPushButton *defaultButton = msgBox.addButton(QLatin1String("Debug with default debugger"), QMessageBox::AcceptRole);
@@ -416,8 +445,10 @@ bool chooseDebugger(QString *errorMessage)
                               && !defaultDebugger.isEmpty());
     msgBox.exec();
     if (msgBox.clickedButton() == creatorButton) {
-        // Just in case, default to standard
-        if (startCreatorAsDebugger(errorMessage))
+        // Just in case, default to standard. Do not run as client in the unlikely case
+        // Creator crashed
+        const bool canRunAsClient = !processName.contains(QLatin1String(creatorBinaryC), Qt::CaseInsensitive);
+        if (startCreatorAsDebugger(canRunAsClient, errorMessage))
             return true;
         return startDefaultDebugger(errorMessage);
     }
@@ -552,7 +583,7 @@ int main(int argc, char *argv[])
         usage(QCoreApplication::applicationFilePath(), errorMessage);
         break;
     case ForceCreatorMode:
-        ex = startCreatorAsDebugger(&errorMessage) ? 0 : -1;
+        ex = startCreatorAsDebugger(true, &errorMessage) ? 0 : -1;
         break;
     case ForceDefaultMode:
         ex = startDefaultDebugger(&errorMessage) ? 0 : -1;