Crash: Fix crash when removing a tool chain

Fix crash on trying to debug an application after the last
tool chain for the Qt version used was removed.

Task-number: QTCREATORBUG-4197
Reviewed-by: dt

src/plugins/projectexplorer/buildconfiguration.cpp

@@ -72,6 +72,11 @@ BuildConfiguration::BuildConfiguration(Target *target, const QString &id) :
     //: Display name of the clean build step list. Used as part of the labels in the project window.
     bsl->setDefaultDisplayName(tr("Clean"));
     m_stepLists.append(bsl);
+
+    connect(ToolChainManager::instance(), SIGNAL(toolChainRemoved(ProjectExplorer::ToolChain*)),
+            this, SLOT(handleToolChainRemovals(ProjectExplorer::ToolChain*)));
+    connect(ToolChainManager::instance(), SIGNAL(toolChainAdded(ProjectExplorer::ToolChain*)),
+            this, SLOT(handleToolChainAddition(ProjectExplorer::ToolChain*)));
 }
 
 BuildConfiguration::BuildConfiguration(Target *target, BuildConfiguration *source) :
@@ -85,6 +90,11 @@ BuildConfiguration::BuildConfiguration(Target *target, BuildConfiguration *sourc
     // Do not clone stepLists here, do that in the derived constructor instead
     // otherwise BuildStepFactories might reject to set up a BuildStep for us
     // since we are not yet the derived class!
+
+    connect(ToolChainManager::instance(), SIGNAL(toolChainRemoved(ProjectExplorer::ToolChain*)),
+            this, SLOT(handleToolChainRemovals(ProjectExplorer::ToolChain*)));
+    connect(ToolChainManager::instance(), SIGNAL(toolChainAdded(ProjectExplorer::ToolChain*)),
+            this, SLOT(handleToolChainAddition(ProjectExplorer::ToolChain*)));
 }
 
 BuildConfiguration::~BuildConfiguration()
@@ -155,6 +165,22 @@ bool BuildConfiguration::fromMap(const QVariantMap &map)
     return ProjectConfiguration::fromMap(map);
 }
 
+void BuildConfiguration::handleToolChainRemovals(ProjectExplorer::ToolChain *tc)
+{
+    if (m_toolChain != tc)
+        return;
+    setToolChain(target()->preferredToolChain(this));
+}
+
+void BuildConfiguration::handleToolChainAddition(ProjectExplorer::ToolChain *tc)
+{
+    Q_UNUSED(tc);
+    if (m_toolChain != 0)
+        return;
+    setToolChain(target()->preferredToolChain(this));
+}
+
+
 Target *BuildConfiguration::target() const
 {
     return static_cast<Target *>(parent());

src/plugins/projectexplorer/buildconfiguration.h

@@ -120,6 +120,10 @@ protected:
 
     virtual bool fromMap(const QVariantMap &map);
 
+private slots:
+    void handleToolChainRemovals(ProjectExplorer::ToolChain *tc);
+    void handleToolChainAddition(ProjectExplorer::ToolChain *tc);
+
 private:
     bool m_clearSystemEnvironment;
     QList<Utils::EnvironmentItem> m_userEnvironmentChanges;

src/plugins/qt4projectmanager/qt4buildconfiguration.cpp

@@ -369,8 +369,7 @@ void Qt4BuildConfiguration::setQtVersion(QtVersion *version)
 void Qt4BuildConfiguration::setToolChain(ProjectExplorer::ToolChain *tc)
 {
     Q_ASSERT(qtVersion());
-    if (!qt4Target()->possibleToolChains(this).contains(tc)
-            || tc->restrictedToTargets().contains(target()->id()))
+    if (tc != 0 && !qt4Target()->possibleToolChains(this).contains(tc))
         return;
 
     BuildConfiguration::setToolChain(tc);

src/plugins/qt4projectmanager/qt4projectconfigwidget.cpp

@@ -463,8 +463,13 @@ void Qt4ProjectConfigWidget::toolChainChanged()
             m_ignoreChange = true;
             m_ui->toolChainComboBox->setCurrentIndex(i);
             m_ignoreChange = false;
+            return;
         }
     }
+    m_ignoreChange = true;
+    m_ui->toolChainComboBox->addItem(tr("<No tool chain selected>"), qVariantFromValue(static_cast<void *>(0)));
+    m_ui->toolChainComboBox->setCurrentIndex(m_ui->toolChainComboBox->count() - 1);
+    m_ignoreChange = false;
 }
 
 void Qt4ProjectConfigWidget::updateToolChainCombo()
@@ -476,20 +481,8 @@ void Qt4ProjectConfigWidget::updateToolChainCombo()
     foreach (ProjectExplorer::ToolChain *toolchain, toolchains)
         m_ui->toolChainComboBox->addItem(toolchain->displayName(),
                                          qVariantFromValue(static_cast<void *>(toolchain)));
-    m_ignoreChange = true;
-    if (!m_buildConfiguration->toolChain() || toolchains.isEmpty()) {
-        m_ui->toolChainComboBox->addItem(tr("<Invalid tool chain>"), qVariantFromValue(static_cast<void *>(0)));
-        m_ui->toolChainComboBox->setCurrentIndex(m_ui->toolChainComboBox->count() - 1);
-    } else if (toolchains.contains(m_buildConfiguration->toolChain())) {
-        m_ui->toolChainComboBox->setCurrentIndex(toolchains.indexOf(m_buildConfiguration->toolChain()));
-    } else { // reset to some sensible tool chain
-        ToolChain *tc = 0;
-        if (!toolchains.isEmpty())
-            tc = toolchains.at(0);
-        m_buildConfiguration->setToolChain(tc);
-    }
-    m_ignoreChange = false;
     m_ui->toolChainComboBox->setEnabled(toolchains.size() > 1);
+    toolChainChanged();
 }
 
 void Qt4ProjectConfigWidget::toolChainSelected(int index)