fix several kind of warnings:

+ fix -Wparentheses/-Wlogical-op-parentheses
+ fix -Wunused-variable
+ disable -Wundefined-var-template due to many false-positives (clang)
+ fix -Winconsistent-missing-override
+ fix -Wmaybe-uninitialized

CMakeLists.txt

@@ -101,6 +101,9 @@ if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_COMPILER_IS_CLANGXX)
 endif(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_COMPILER_IS_CLANGXX)
 
 if(CMAKE_COMPILER_IS_CLANGXX)
+    # Disable warning about potentially uninstantiated static members
+    # because it leads to a lot of false-positives.
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-undefined-var-template")
     # older boost.preprocessor turn off variadics for clang
     add_definitions(-DBOOST_PP_VARIADICS=1)
     message(STATUS "Force BOOST_PP_VARIADICS=1 for clang")

src/Gui/QuantitySpinBox.cpp

@@ -289,7 +289,6 @@ void Gui::QuantitySpinBox::setExpression(boost::shared_ptr<Expression> expr)
 
 QString QuantitySpinBox::boundToName() const
 {
-    Q_D(const QuantitySpinBox);
     if (isBound()) {
         std::string path = getPath().toString();
         return QString::fromStdString(path);
@@ -305,7 +304,6 @@ QString QuantitySpinBox::boundToName() const
  */
 void QuantitySpinBox::setBoundToByName(const QString &name)
 {
-    Q_D(QuantitySpinBox);
     try {
         // get document
         App::Document *doc = App::GetApplication().getActiveDocument();
@@ -350,7 +348,6 @@ void QuantitySpinBox::setBoundToByName(const QString &name)
 
 QString Gui::QuantitySpinBox::expressionText() const
 {
-    Q_D(const QuantitySpinBox);
     try {
         if (hasExpression()) {
             return QString::fromStdString(getExpressionString());

src/Mod/Path/App/Area.cpp

@@ -22,6 +22,7 @@
 #include "PreCompiled.h"
 
 #ifndef _PreComp_
+# include <cfloat>
 #endif
 
 #include <boost/version.hpp>
@@ -2804,9 +2805,8 @@ std::list<TopoDS_Shape> Area::sortWires(const std::list<TopoDS_Shape> &shapes,
     double max_dist = sort_mode==SortModeGreedy?threshold*threshold:0;
     while(shape_list.size()) {
         AREA_TRACE("sorting " << shape_list.size() << ' ' << AREA_XYZ(pstart));
-        double best_d;
+        double best_d = DBL_MAX;
         auto best_it = shape_list.begin();
-        bool first = true;
         for(auto it=best_it;it!=shape_list.end();++it) {
             double d;
             gp_Pnt pt;
@@ -2814,8 +2814,7 @@ std::list<TopoDS_Shape> Area::sortWires(const std::list<TopoDS_Shape> &shapes,
                 d = it->myPln.SquareDistance(pstart);
             else
                 d = it->nearest(pstart);
-            if(first || d<best_d) {
-                first = false;
+            if(d < best_d) {
                 best_it = it;
                 best_d = d;
             }

src/Mod/Sketcher/Gui/ViewProviderSketch.cpp

@@ -2463,7 +2463,7 @@ void ViewProviderSketch::doBoxSelection(const SbVec2s &startPos, const SbVec2s &
             // forces the user to select much more than the curve (all the poles) and it would not select the curve in cases
             // where it is indeed comprised in the box.
             // The implementation of the touch mode is also far from a desirable "touch" as it only recognizes touched points not the curve itself
-            if (pnt1Inside && pnt2Inside || (touchMode && (pnt1Inside || pnt2Inside))) {
+            if ((pnt1Inside && pnt2Inside) || (touchMode && (pnt1Inside || pnt2Inside))) {
                 std::stringstream ss;
                 ss << "Edge" << GeoId + 1;
                 Gui::Selection().addSelection(doc->getName(), sketchObject->getNameInDocument(), ss.str().c_str());

src/Mod/TechDraw/App/DrawViewMulti.h

@@ -50,7 +50,7 @@ namespace TechDraw
  */
 class TechDrawExport DrawViewMulti : public DrawViewPart
 {
-    PROPERTY_HEADER(Part::DrawViewMulti);
+    PROPERTY_HEADER_WITH_OVERRIDE(Part::DrawViewMulti);
 
 public:
     /// Constructor