diff --git a/CMakeLists.txt b/CMakeLists.txt
index fec9660856..f4dabf7657 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -27,6 +27,7 @@ set(PACKAGE_VERSION "${PACKAGE_VERSION_MAJOR}.${PACKAGE_VERSION_MINOR}.${PACKAGE
 set(PACKAGE_STRING "${PROJECT_NAME} ${PACKAGE_VERSION}")
 
 # include local modules
+include(CheckCXXCompilerFlag)
 include(AddFileDependencies)
 include(cMake/FreeCadMacros.cmake)
 # include helper functions/macros
diff --git a/src/3rdParty/salomesmesh/CMakeLists.txt b/src/3rdParty/salomesmesh/CMakeLists.txt
index d58d078e4f..f0532e8852 100644
--- a/src/3rdParty/salomesmesh/CMakeLists.txt
+++ b/src/3rdParty/salomesmesh/CMakeLists.txt
@@ -9,11 +9,22 @@ SET(SMESH_VERSION_TWEAK 0)
 if(CMAKE_COMPILER_IS_GNUCXX)
     set(CMAKE_CXX_FLAGS " ${CMAKE_CXX_FLAGS} -Wno-sign-compare -Wno-reorder -Wno-switch -Wno-unused-variable -Wno-unused-but-set-variable -Wno-comment -Wno-unused-parameter -Wno-empty-body -Wno-pedantic")
 elseif(CMAKE_COMPILER_IS_CLANGXX)
-    set(CMAKE_CXX_FLAGS " ${CMAKE_CXX_FLAGS} -Wno-sign-compare -Wno-reorder -Wno-switch -Wno-unused-variable -Wno-unused-private-field -Wno-unused-function -Wno-sometimes-uninitialized -Wno-overloaded-virtual -Wno-dynamic-class-memaccess -Wno-comment -Wno-unused-parameter -Wno-extra-semi")
+    set(CMAKE_CXX_FLAGS " ${CMAKE_CXX_FLAGS} -Wno-self-assign -Wno-sign-compare -Wno-logical-op-parentheses -Wno-reorder -Wno-switch -Wno-switch-enum -Wno-unknown-pragmas -Wno-unused-variable -Wno-unused-private-field")
+    set(CMAKE_CXX_FLAGS " ${CMAKE_CXX_FLAGS} -Wno-unused-function -Wno-sometimes-uninitialized -Wno-overloaded-virtual -Wno-dynamic-class-memaccess -Wno-comment -Wno-unused-parameter -Wno-extra-semi")
 endif()
 
 if(CMAKE_COMPILER_IS_CLANGXX)
-    set(CMAKE_CXX_FLAGS " ${CMAKE_CXX_FLAGS} -Wno-self-assign -Wno-reorder -Wno-switch-enum -Wno-unknown-pragmas -Wno-logical-op-parentheses -Wno-unused-variable -Wno-unused-function -Wno-overloaded-virtual")
+    unset(_flag_found CACHE)
+    check_cxx_compiler_flag("-Wno-deprecated-copy" _flag_found)
+    if (_flag_found)
+        set(CMAKE_CXX_FLAGS " ${CMAKE_CXX_FLAGS} -Wno-deprecated-copy")
+    endif ()
+
+    unset(_flag_found CACHE)
+    check_cxx_compiler_flag("-Wno-missing-field-initializers" _flag_found)
+    if (_flag_found)
+        set(CMAKE_CXX_FLAGS " ${CMAKE_CXX_FLAGS} -Wno-missing-field-initializers")
+    endif ()
 endif()
 
 if (VTK_OPTIONS)
diff --git a/src/3rdParty/salomesmesh/src/SMESH/SMESH_MeshEditor.cpp b/src/3rdParty/salomesmesh/src/SMESH/SMESH_MeshEditor.cpp
index 4386473fcb..fcd044b00f 100644
--- a/src/3rdParty/salomesmesh/src/SMESH/SMESH_MeshEditor.cpp
+++ b/src/3rdParty/salomesmesh/src/SMESH/SMESH_MeshEditor.cpp
@@ -4168,7 +4168,7 @@ void SMESH_MeshEditor::Smooth (TIDSortedElemSet &          theElems,
             // if ( posType != SMDS_TOP_3DSPACE )
             //   dist2 = pNode.SquareDistance( surface->Value( newUV.X(), newUV.Y() ));
             // if ( dist2 < dist1 )
-              uv = newUV;
+            uv = newUV;
           }
         }
         // store UV in the map
diff --git a/src/App/Expression.cpp b/src/App/Expression.cpp
index 038562f497..fc4503b977 100644
--- a/src/App/Expression.cpp
+++ b/src/App/Expression.cpp
@@ -350,23 +350,25 @@ static inline bool definitelyLessThan(T a, T b)
 
 static inline int essentiallyInteger(double a, long &l, int &i) {
     double intpart;
-    if(std::modf(a,&intpart) == 0.0) {
-        if(intpart<0.0) {
-            if(intpart >= INT_MIN) {
-                i = (int)intpart;
+    if (std::modf(a,&intpart) == 0.0) {
+        if (intpart<0.0) {
+            if (intpart >= INT_MIN) {
+                i = static_cast<int>(intpart);
                 l = i;
                 return 1;
             }
-            if(intpart >= LONG_MIN) {
-                l = (long)intpart;
+            if (intpart >= LONG_MIN) {
+                l = static_cast<long>(intpart);
                 return 2;
             }
-        }else if(intpart <= INT_MAX) {
-            i = (int)intpart;
+        }
+        else if (intpart <= INT_MAX) {
+            i = static_cast<int>(intpart);
             l = i;
             return 1;
-        }else if(intpart <= LONG_MAX) {
-            l = (int)intpart;
+        }
+        else if (intpart <= static_cast<double>(LONG_MAX)) {
+            l = static_cast<int>(intpart);
             return 2;
         }
     }
@@ -375,14 +377,15 @@ static inline int essentiallyInteger(double a, long &l, int &i) {
 
 static inline bool essentiallyInteger(double a, long &l) {
     double intpart;
-    if(std::modf(a,&intpart) == 0.0) {
-        if(intpart<0.0) {
-            if(intpart >= LONG_MIN) {
-                l = (long)intpart;
+    if (std::modf(a,&intpart) == 0.0) {
+        if (intpart<0.0) {
+            if (intpart >= LONG_MIN) {
+                l = static_cast<long>(intpart);
                 return true;
             }
-        }else if(intpart <= LONG_MAX) {
-            l = (long)intpart;
+        }
+        else if (intpart <= static_cast<double>(LONG_MAX)) {
+            l = static_cast<long>(intpart);
             return true;
         }
     }
diff --git a/src/Gui/NaviCube.cpp b/src/Gui/NaviCube.cpp
index 2690031d42..1b5d56243b 100644
--- a/src/Gui/NaviCube.cpp
+++ b/src/Gui/NaviCube.cpp
@@ -114,6 +114,12 @@
 # include <QOpenGLTexture>
 #endif
 
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 //#include <OpenGL/glu.h>
 #include <Eigen/Dense>
 #include <vector>
diff --git a/src/Gui/WorkbenchPyImp.cpp b/src/Gui/WorkbenchPyImp.cpp
index bae0d5ea0e..2cd3001363 100644
--- a/src/Gui/WorkbenchPyImp.cpp
+++ b/src/Gui/WorkbenchPyImp.cpp
@@ -117,9 +117,9 @@ PyObject* WorkbenchPy::getToolbarItems(PyObject *args)
         std::list<std::pair<std::string, std::list<std::string>>> bars = getWorkbenchPtr()->getToolbarItems();
 
         Py::Dict dict;
-        for (const auto it : bars) {
+        for (const auto& it : bars) {
             Py::List list;
-            for (const auto jt : it.second) {
+            for (const auto& jt : it.second) {
                 list.append(Py::String(jt));
             }
             dict.setItem(it.first, list);
diff --git a/src/Mod/Mesh/App/Core/Approximation.cpp b/src/Mod/Mesh/App/Core/Approximation.cpp
index a115792c2d..42494427ef 100644
--- a/src/Mod/Mesh/App/Core/Approximation.cpp
+++ b/src/Mod/Mesh/App/Core/Approximation.cpp
@@ -29,6 +29,12 @@
 # include <iterator> 
 #endif
 
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 #include "Approximation.h"
 #include "Elements.h"
 #include "Utilities.h"
diff --git a/src/Mod/Mesh/App/Core/CylinderFit.cpp b/src/Mod/Mesh/App/Core/CylinderFit.cpp
index d5bfb3480f..6b46b6baec 100644
--- a/src/Mod/Mesh/App/Core/CylinderFit.cpp
+++ b/src/Mod/Mesh/App/Core/CylinderFit.cpp
@@ -61,6 +61,12 @@
 # include <iterator> 
 #endif
 
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 #include "CylinderFit.h"
 #include <Base/Console.h>
 #include <Mod/Mesh/App/WildMagic4/Wm4ApprLineFit3.h>
diff --git a/src/Mod/Mesh/App/Core/KDTree.cpp b/src/Mod/Mesh/App/Core/KDTree.cpp
index c7a7f72377..5c8d126cf9 100644
--- a/src/Mod/Mesh/App/Core/KDTree.cpp
+++ b/src/Mod/Mesh/App/Core/KDTree.cpp
@@ -28,6 +28,12 @@
 #ifndef _PreComp_
 #endif
 
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 #include "KDTree.h"
 #include <kdtree++/kdtree.hpp>
 
diff --git a/src/Mod/Mesh/App/Core/SphereFit.cpp b/src/Mod/Mesh/App/Core/SphereFit.cpp
index dfc1166858..fcf0cdcc53 100644
--- a/src/Mod/Mesh/App/Core/SphereFit.cpp
+++ b/src/Mod/Mesh/App/Core/SphereFit.cpp
@@ -28,6 +28,12 @@
 # include <iterator> 
 #endif
 
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 #include "SphereFit.h"
 #include <Base/Console.h>
 
diff --git a/src/Mod/Part/App/GeometryCurvePyImp.cpp b/src/Mod/Part/App/GeometryCurvePyImp.cpp
index b2cd23f61d..16b424eebc 100644
--- a/src/Mod/Part/App/GeometryCurvePyImp.cpp
+++ b/src/Mod/Part/App/GeometryCurvePyImp.cpp
@@ -22,6 +22,13 @@
 
 
 #include "PreCompiled.h"
+
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 #ifndef _PreComp_
 # include <sstream>
 # include <BRepBuilderAPI_MakeEdge.hxx>
diff --git a/src/Mod/Part/App/GeometrySurfacePyImp.cpp b/src/Mod/Part/App/GeometrySurfacePyImp.cpp
index a75a0a961d..c4bb984e77 100644
--- a/src/Mod/Part/App/GeometrySurfacePyImp.cpp
+++ b/src/Mod/Part/App/GeometrySurfacePyImp.cpp
@@ -22,6 +22,13 @@
 
 
 #include "PreCompiled.h"
+
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 #ifndef _PreComp_
 # include <BRepBuilderAPI_MakeFace.hxx>
 # include <gp_Circ.hxx>
diff --git a/src/Mod/ReverseEngineering/Gui/SegmentationManual.cpp b/src/Mod/ReverseEngineering/Gui/SegmentationManual.cpp
index d7ff195dac..510aef8744 100644
--- a/src/Mod/ReverseEngineering/Gui/SegmentationManual.cpp
+++ b/src/Mod/ReverseEngineering/Gui/SegmentationManual.cpp
@@ -151,7 +151,7 @@ static void findGeometry(int minFaces, double tolerance,
 
                 for (auto segmIt : segm) {
                     const std::vector<MeshCore::MeshSegment>& data = segmIt->GetSegments();
-                    for (const auto dataIt : data) {
+                    for (const auto& dataIt : data) {
                         vpm->addSelection(dataIt);
                     }
                 }
diff --git a/src/Mod/Robot/App/CMakeLists.txt b/src/Mod/Robot/App/CMakeLists.txt
index f794c28112..383386c01b 100644
--- a/src/Mod/Robot/App/CMakeLists.txt
+++ b/src/Mod/Robot/App/CMakeLists.txt
@@ -125,6 +125,12 @@ SOURCE_GROUP("Module" FILES ${Mod_SRCS})
 add_library(Robot SHARED ${Robot_SRCS})
 target_link_libraries(Robot ${Robot_LIBS})
 
+unset(_flag_found CACHE)
+check_cxx_compiler_flag("-Wno-deprecated-copy" _flag_found)
+if (_flag_found)
+  target_compile_options(Robot PRIVATE -Wno-deprecated-copy)
+endif()
+
 SET_BIN_DIR(Robot Robot /Mod/Robot)
 SET_PYTHON_PREFIX_SUFFIX(Robot)
 
diff --git a/src/Mod/Robot/Gui/CMakeLists.txt b/src/Mod/Robot/Gui/CMakeLists.txt
index 7aea7b2639..e460a69d9c 100644
--- a/src/Mod/Robot/Gui/CMakeLists.txt
+++ b/src/Mod/Robot/Gui/CMakeLists.txt
@@ -156,6 +156,12 @@ SET(RobotGuiIcon_SVG
 add_library(RobotGui SHARED ${RobotGui_SRCS} ${RobotGuiIcon_SVG})
 target_link_libraries(RobotGui ${RobotGui_LIBS})
 
+unset(_flag_found CACHE)
+check_cxx_compiler_flag("-Wno-deprecated-copy" _flag_found)
+if (_flag_found)
+    target_compile_options(RobotGui PRIVATE -Wno-deprecated-copy)
+endif ()
+
 
 SET_BIN_DIR(RobotGui RobotGui /Mod/Robot)
 SET_PYTHON_PREFIX_SUFFIX(RobotGui)
diff --git a/src/Mod/Sketcher/App/planegcs/GCS.cpp b/src/Mod/Sketcher/App/planegcs/GCS.cpp
index 76ecb4fef5..a65dc65825 100644
--- a/src/Mod/Sketcher/App/planegcs/GCS.cpp
+++ b/src/Mod/Sketcher/App/planegcs/GCS.cpp
@@ -25,6 +25,12 @@
 #pragma warning(disable : 4996)
 #endif
 
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 //#define _GCS_DEBUG
 //#define _GCS_DEBUG_SOLVER_JACOBIAN_QR_DECOMPOSITION_TRIANGULAR_MATRIX
 //#define _DEBUG_TO_FILE // Many matrices surpass the report view string size.
diff --git a/src/Mod/Sketcher/App/planegcs/qp_eq.cpp b/src/Mod/Sketcher/App/planegcs/qp_eq.cpp
index 7eeb58fafc..3133937b7e 100644
--- a/src/Mod/Sketcher/App/planegcs/qp_eq.cpp
+++ b/src/Mod/Sketcher/App/planegcs/qp_eq.cpp
@@ -24,6 +24,12 @@
 #pragma warning(disable : 4244)
 #endif
 
+#if defined(__clang__) && defined(__has_warning)
+#if __has_warning("-Wdeprecated-copy")
+# pragma clang diagnostic ignored "-Wdeprecated-copy"
+#endif
+#endif
+
 #include <iostream>
 #include <Eigen/QR>
 
diff --git a/src/zipios++/ziphead.cpp b/src/zipios++/ziphead.cpp
index dc6f323c6d..749661d294 100644
--- a/src/zipios++/ziphead.cpp
+++ b/src/zipios++/ziphead.cpp
@@ -198,7 +198,7 @@ bool ZipLocalEntry::trailingDataDescriptor() const {
   // gp_bitfield bit 3 is one, if this entry uses a trailing data
   // descriptor to keep size, compressed size and crc-32
   // fields.
-  if ( ( gp_bitfield & 4 ) == 1 )
+  if ( ( gp_bitfield & 4 ) == 4 )
     return true ;
   else
     return false ;