Fixed Clang 12 compiler warnings.

CMakeLists.txt

@@ -239,6 +239,11 @@ if (NOT MSVC AND ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU" OR "${CMAKE_CXX_COMP
         add_compile_options(-Wno-deprecated-declarations)
     endif()
 
+    # Clang reports misleading indentation for some IF blocks because of mixing tabs with spaces.
+    if("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+        add_compile_options(-Wno-misleading-indentation)
+    endif()
+
     #GCC generates loads of -Wunknown-pragmas when compiling igl. The fix is not easy due to a bug in gcc, see
     # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66943 or
     # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53431

src/libslic3r/Fill/FillRectilinear.cpp

@@ -2391,7 +2391,7 @@ static std::vector<MonotonicRegionLink> chain_monotonic_regions(
 
     // Probability (unnormalized) of traversing a link between two monotonic regions.
 	auto path_probability = [
-#ifndef __APPLE__
+#if !defined(__APPLE__) && !defined(__clang__)
         // clang complains when capturing constexpr constants.
         pheromone_alpha, pheromone_beta
 #endif // __APPLE__

src/libslic3r/Model.cpp

@@ -2264,7 +2264,7 @@ void check_model_ids_validity(const Model &model)
         for (const ModelInstance *model_instance : model_object->instances)
             check(model_instance->id());
     }
-    for (const auto mm : model.materials) {
+    for (const auto &mm : model.materials) {
         check(mm.second->id());
         check(mm.second->config.id());
     }

src/libslic3r/MultiPoint.hpp

@@ -17,7 +17,8 @@ class MultiPoint
 public:
     Points points;
     
-    MultiPoint() {}
+    MultiPoint() = default;
+    virtual ~MultiPoint() = default;
     MultiPoint(const MultiPoint &other) : points(other.points) {}
     MultiPoint(MultiPoint &&other) : points(std::move(other.points)) {}
     MultiPoint(std::initializer_list<Point> list) : points(list) {}

src/libslic3r/Polygon.hpp

@@ -19,7 +19,7 @@ class Polygon : public MultiPoint
 {
 public:
     Polygon() = default;
-    virtual ~Polygon() = default;
+    ~Polygon() override = default;
     explicit Polygon(const Points &points) : MultiPoint(points) {}
 	Polygon(std::initializer_list<Point> points) : MultiPoint(points) {}
     Polygon(const Polygon &other) : MultiPoint(other.points) {}

src/libslic3r/Polyline.hpp

@@ -16,7 +16,8 @@ typedef std::vector<ThickPolyline> ThickPolylines;
 
 class Polyline : public MultiPoint {
 public:
-    Polyline() {};
+    Polyline() = default;
+    ~Polyline() override = default;
     Polyline(const Polyline &other) : MultiPoint(other.points) {}
     Polyline(Polyline &&other) : MultiPoint(std::move(other.points)) {}
     Polyline(std::initializer_list<Point> list) : MultiPoint(list) {}

src/slic3r/GUI/FirmwareDialog.cpp

@@ -654,7 +654,7 @@ void FirmwareDialog::priv::perform_upload()
 			}
 		})
 		.on_message([
-#ifndef __APPLE__
+#if !defined(__APPLE__) && !defined(__clang__)
 	        // clang complains when capturing constants.
 			extra_verbose,
 #endif // __APPLE__

src/slic3r/GUI/OptionsGroup.hpp

@@ -185,7 +185,7 @@ public:
 
 	OptionsGroup(	wxWindow* _parent, const wxString& title, bool is_tab_opt = false, 
                     column_t extra_clmn = nullptr);
-	~OptionsGroup() { clear(true); }
+	virtual ~OptionsGroup() { clear(true); }
 
     wxGridSizer*        get_grid_sizer() { return m_grid_sizer; }
 	const std::vector<Line>& get_lines() { return m_lines; }
@@ -253,6 +253,7 @@ public:
 		OptionsGroup(parent, title, is_tab_opt, extra_clmn), m_config(&config->get()), m_modelconfig(config) {}
 	ConfigOptionsGroup(	wxWindow* parent) :
 		OptionsGroup(parent, wxEmptyString, true, nullptr) {}
+    ~ConfigOptionsGroup() override = default;
 
 	const wxString& config_category() const throw() { return m_config_category; }
 	int config_type() const throw() { return m_config_type; }