diff --git a/src/App/Application.h b/src/App/Application.h
index c9d5f1229d..189444d28c 100644
--- a/src/App/Application.h
+++ b/src/App/Application.h
@@ -488,7 +488,7 @@ protected:
 
 private:
     /// Constructor
-    Application(std::map<std::string,std::string> &mConfig);
+    explicit Application(std::map<std::string,std::string> &mConfig);
     /// Destructor
     virtual ~Application();
 
diff --git a/src/App/ColorModel.h b/src/App/ColorModel.h
index a9b4b5d292..b38a79fb4b 100644
--- a/src/App/ColorModel.h
+++ b/src/App/ColorModel.h
@@ -74,7 +74,7 @@ class AppExport ColorModel
 {
 public:
     ColorModel() = default;
-    ColorModel (std::size_t usCt) {
+    explicit ColorModel (std::size_t usCt) {
         colors.resize(usCt);
     }
     ColorModel(const ColorModel&) = default;
diff --git a/src/App/Document.cpp b/src/App/Document.cpp
index d5af1f0449..817ce571dd 100644
--- a/src/App/Document.cpp
+++ b/src/App/Document.cpp
@@ -328,7 +328,7 @@ void Document::exportGraphviz(std::ostream& out) const
     class GraphCreator {
     public:
 
-        GraphCreator(struct DocumentP* _d) : d(_d), vertex_no(0), seed(std::random_device()()), distribution(0,255) {
+        explicit GraphCreator(struct DocumentP* _d) : d(_d), vertex_no(0), seed(std::random_device()()), distribution(0,255) {
             build();
         }
 
@@ -1793,7 +1793,7 @@ static DocExportStatus _ExportStatus;
 // Exception-safe exporting status setter
 class DocumentExporting {
 public:
-    DocumentExporting(const std::vector<App::DocumentObject*> &objs) {
+    explicit DocumentExporting(const std::vector<App::DocumentObject*> &objs) {
         _ExportStatus.status = Document::Exporting;
         _ExportStatus.objs.insert(objs.begin(),objs.end());
     }
diff --git a/src/App/Document.h b/src/App/Document.h
index a576decd17..1a81d28033 100644
--- a/src/App/Document.h
+++ b/src/App/Document.h
@@ -510,7 +510,7 @@ public:
 
 protected:
     /// Construction
-    Document(const char *name = "");
+    explicit Document(const char *name = "");
 
     void _removeObject(DocumentObject* pcObject);
     void _addObject(DocumentObject* pcObject, const char* pObjectName);
diff --git a/src/App/DocumentObject.h b/src/App/DocumentObject.h
index 31c1e0920d..e863958edc 100644
--- a/src/App/DocumentObject.h
+++ b/src/App/DocumentObject.h
@@ -74,11 +74,11 @@ enum ObjectStatus {
 class AppExport DocumentObjectExecReturn
 {
 public:
-    DocumentObjectExecReturn(const std::string& sWhy, DocumentObject* WhichObject=nullptr)
+    explicit DocumentObjectExecReturn(const std::string& sWhy, DocumentObject* WhichObject=nullptr)
         : Why(sWhy), Which(WhichObject)
     {
     }
-    DocumentObjectExecReturn(const char* sWhy, DocumentObject* WhichObject=nullptr)
+    explicit DocumentObjectExecReturn(const char* sWhy, DocumentObject* WhichObject=nullptr)
         : Which(WhichObject)
     {
         if (sWhy)
diff --git a/src/App/DocumentObjectPyImp.cpp b/src/App/DocumentObjectPyImp.cpp
index bf409ba338..7410320ae9 100644
--- a/src/App/DocumentObjectPyImp.cpp
+++ b/src/App/DocumentObjectPyImp.cpp
@@ -476,7 +476,7 @@ PyObject* DocumentObjectPy::getSubObject(PyObject *args, PyObject *keywds)
         Py::Object obj;
         Py::Object pyObj;
         Base::Matrix4D mat;
-        SubInfo(const Base::Matrix4D &mat) : sobj(nullptr), mat(mat){}
+        explicit SubInfo(const Base::Matrix4D &mat) : sobj(nullptr), mat(mat){}
     };
 
     Base::Matrix4D mat;
diff --git a/src/App/DocumentObserver.cpp b/src/App/DocumentObserver.cpp
index e102333672..eead2a0769 100644
--- a/src/App/DocumentObserver.cpp
+++ b/src/App/DocumentObserver.cpp
@@ -544,7 +544,7 @@ std::string PropertyLinkT::getPropertyPython() const
 
 class DocumentWeakPtrT::Private {
 public:
-    Private(App::Document* doc) : _document(doc) {
+    explicit Private(App::Document* doc) : _document(doc) {
         if (doc) {
             connectApplicationDeletedDocument = App::GetApplication().signalDeleteDocument.connect(std::bind
                 (&Private::deletedDocument, this, sp::_1));
@@ -596,7 +596,7 @@ App::Document* DocumentWeakPtrT::operator->() const noexcept
 
 class DocumentObjectWeakPtrT::Private {
 public:
-    Private(App::DocumentObject* obj) : object(obj), indocument(false) {
+    explicit Private(App::DocumentObject* obj) : object(obj), indocument(false) {
         set(obj);
     }
     void deletedDocument(const App::Document& doc) {
diff --git a/src/App/DocumentObserver.h b/src/App/DocumentObserver.h
index 5d4b580584..7b27ae61dc 100644
--- a/src/App/DocumentObserver.h
+++ b/src/App/DocumentObserver.h
@@ -49,9 +49,9 @@ public:
     /*! Constructor */
     DocumentT();
     /*! Constructor */
-    DocumentT(Document*);
+    DocumentT(Document*); // explicit bombs
     /*! Constructor */
-    DocumentT(const std::string&);
+    explicit DocumentT(const std::string&);
     /*! Constructor */
     DocumentT(const DocumentT&);
     /*! Destructor */
@@ -99,13 +99,13 @@ public:
     /*! Constructor */
     DocumentObjectT(DocumentObjectT &&);
     /*! Constructor */
-    DocumentObjectT(const DocumentObject*);
+    explicit DocumentObjectT(const DocumentObject*);
     /*! Constructor */
     DocumentObjectT(const Document*, const std::string& objName);
     /*! Constructor */
     DocumentObjectT(const char *docName, const char *objName);
     /*! Constructor */
-    DocumentObjectT(const Property*);
+    explicit DocumentObjectT(const Property*);
     /*! Destructor */
     ~DocumentObjectT();
     /*! Assignment operator */
@@ -177,7 +177,7 @@ public:
     SubObjectT(const DocumentObject*, const char *subname);
 
     /*! Constructor */
-    SubObjectT(const DocumentObject*);
+    SubObjectT(const DocumentObject*);// explicit bombs
 
     /*! Constructor */
     SubObjectT(const char *docName, const char *objName, const char *subname);
@@ -257,13 +257,13 @@ public:
     PropertyLinkT();
 
     /*! Constructor */
-    PropertyLinkT(DocumentObject *obj);
+    PropertyLinkT(DocumentObject *obj);// explicit bombs
 
     /*! Constructor */
     PropertyLinkT(DocumentObject *obj, const std::vector<std::string>& subNames);
 
     /*! Constructor */
-    PropertyLinkT(const std::vector<DocumentObject*>& objs);
+    explicit PropertyLinkT(const std::vector<DocumentObject*>& objs);
 
     /*! Constructor */
     PropertyLinkT(const std::vector<DocumentObject*>& objs, const std::vector<std::string>& subNames);
@@ -281,7 +281,7 @@ private:
 class AppExport DocumentWeakPtrT
 {
 public:
-    DocumentWeakPtrT(App::Document*) noexcept;
+    explicit DocumentWeakPtrT(App::Document*) noexcept;
     ~DocumentWeakPtrT();
 
     /*!
@@ -320,7 +320,7 @@ private:
 class AppExport DocumentObjectWeakPtrT
 {
 public:
-    DocumentObjectWeakPtrT(App::DocumentObject*);
+    explicit DocumentObjectWeakPtrT(App::DocumentObject*);
     ~DocumentObjectWeakPtrT();
 
     /*!
@@ -383,7 +383,7 @@ template <class T>
 class WeakPtrT
 {
 public:
-    WeakPtrT(T* t) : ptr(t) {
+    explicit WeakPtrT(T* t) : ptr(t) {
     }
     ~WeakPtrT() = default;
 
@@ -466,7 +466,7 @@ class AppExport DocumentObserver
 public:
     /// Constructor
     DocumentObserver();
-    DocumentObserver(Document*);
+    explicit DocumentObserver(Document*);
     virtual ~DocumentObserver();
 
     /** Attaches to another document, the old document
diff --git a/src/App/Enumeration.cpp b/src/App/Enumeration.cpp
index 8a31b29ca1..1d85767232 100644
--- a/src/App/Enumeration.cpp
+++ b/src/App/Enumeration.cpp
@@ -34,7 +34,7 @@ using namespace App;
 
 namespace {
 struct StringCopy : public Enumeration::Object {
-    StringCopy(const char* str) : d(str) {
+    explicit StringCopy(const char* str) : d(str) {
     }
     const char* data() const override {
         return d.data();
@@ -51,7 +51,7 @@ private:
 };
 
 struct StringView : public Enumeration::Object {
-    StringView(const char* str) : d(str) {
+    explicit StringView(const char* str) : d(str) {
     }
     const char* data() const override {
         return d.data();
diff --git a/src/App/Enumeration.h b/src/App/Enumeration.h
index 1256e2719b..64320ac9b4 100644
--- a/src/App/Enumeration.h
+++ b/src/App/Enumeration.h
@@ -68,7 +68,7 @@ namespace App
         Enumeration(const Enumeration& other);
 
         /// Constructs an Enumeration with a single element
-        Enumeration(const char *valStr);
+        explicit Enumeration(const char *valStr);
 
         /// Constructs an Enumeration using val within list
         Enumeration(const char **list, const char *valStr);
diff --git a/src/App/Expression.cpp b/src/App/Expression.cpp
index 844db1c6b0..e269e8c360 100644
--- a/src/App/Expression.cpp
+++ b/src/App/Expression.cpp
@@ -380,7 +380,7 @@ struct PyObjectWrapper {
 public:
     typedef std::shared_ptr<PyObjectWrapper> Pointer;
 
-    PyObjectWrapper(PyObject *obj):pyobj(obj) {
+    explicit PyObjectWrapper(PyObject *obj):pyobj(obj) {
         Py::_XINCREF(pyobj);
     }
     ~PyObjectWrapper() {
@@ -940,7 +940,7 @@ std::map<App::DocumentObject*,bool> Expression::getDepObjects(std::vector<std::s
 
 class GetIdentifiersExpressionVisitor : public ExpressionVisitor {
 public:
-    GetIdentifiersExpressionVisitor(std::map<App::ObjectIdentifier,bool> &deps)
+    explicit GetIdentifiersExpressionVisitor(std::map<App::ObjectIdentifier,bool> &deps)
         :deps(deps)
     {}
 
@@ -964,7 +964,7 @@ std::map<App::ObjectIdentifier,bool> Expression::getIdentifiers()  const {
 
 class AdjustLinksExpressionVisitor : public ExpressionVisitor {
 public:
-    AdjustLinksExpressionVisitor(const std::set<App::DocumentObject*> &inList)
+    explicit AdjustLinksExpressionVisitor(const std::set<App::DocumentObject*> &inList)
         :inList(inList),res(false)
     {}
 
@@ -985,7 +985,7 @@ bool Expression::adjustLinks(const std::set<App::DocumentObject*> &inList) {
 
 class ImportSubNamesExpressionVisitor : public ExpressionVisitor {
 public:
-    ImportSubNamesExpressionVisitor(const ObjectIdentifier::SubNameMap &subNameMap)
+    explicit ImportSubNamesExpressionVisitor(const ObjectIdentifier::SubNameMap &subNameMap)
         :subNameMap(subNameMap)
     {}
 
@@ -1698,7 +1698,7 @@ TYPESYSTEM_SOURCE(App::FunctionExpression, App::UnitExpression)
 static int _HiddenReference;
 
 struct HiddenReference {
-    HiddenReference(bool cond)
+    explicit HiddenReference(bool cond)
         :cond(cond)
     {
         if(cond)
diff --git a/src/App/Expression.h b/src/App/Expression.h
index 4fa5877fa8..6c77aaef59 100644
--- a/src/App/Expression.h
+++ b/src/App/Expression.h
@@ -80,7 +80,7 @@ protected:
 
 template<class P> class ExpressionModifier : public ExpressionVisitor {
 public:
-    ExpressionModifier(P & _prop)
+    explicit ExpressionModifier(P & _prop)
         : prop(_prop)
         , propLink(Base::freecad_dynamic_cast<App::PropertyLinkBase>(&prop))
         , signaller(_prop,false)
@@ -117,7 +117,7 @@ class AppExport Expression : public Base::BaseClass {
 
 public:
 
-    Expression(const App::DocumentObject * _owner);
+    explicit Expression(const App::DocumentObject * _owner);
 
     ~Expression() override;
 
@@ -164,7 +164,7 @@ public:
 
     class Exception : public Base::Exception {
     public:
-        Exception(const char *sMessage) : Base::Exception(sMessage) { }
+        explicit Exception(const char *sMessage) : Base::Exception(sMessage) { }
     };
 
     App::DocumentObject *  getOwner() const { return owner; }
diff --git a/src/App/ExpressionParser.h b/src/App/ExpressionParser.h
index a2425a6c10..d569c86bcc 100644
--- a/src/App/ExpressionParser.h
+++ b/src/App/ExpressionParser.h
@@ -43,9 +43,9 @@ struct AppExport Expression::Component {
     Expression* e2;
     Expression* e3;
 
-    Component(const std::string &n);
+    explicit Component(const std::string &n);
     Component(Expression *e1, Expression *e2, Expression *e3, bool isRange=false);
-    Component(const ObjectIdentifier::Component &comp);
+    explicit Component(const ObjectIdentifier::Component &comp);
     Component(const Component &other);
     ~Component();
     Component &operator=(const Component &)=delete;
@@ -71,7 +71,7 @@ struct AppExport Expression::Component {
 class  AppExport UnitExpression : public Expression {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 public:
-    UnitExpression(const App::DocumentObject *_owner = nullptr, const Base::Quantity & _quantity = Base::Quantity(), const std::string & _unitStr = std::string());
+    explicit UnitExpression(const App::DocumentObject *_owner = nullptr, const Base::Quantity & _quantity = Base::Quantity(), const std::string & _unitStr = std::string());
 
     ~UnitExpression() override;
 
@@ -111,7 +111,7 @@ private:
 class AppExport NumberExpression : public UnitExpression {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 public:
-    NumberExpression(const App::DocumentObject *_owner = nullptr, const Base::Quantity & quantity = Base::Quantity());
+    explicit NumberExpression(const App::DocumentObject *_owner = nullptr, const Base::Quantity & quantity = Base::Quantity());
 
     Expression * simplify() const override;
 
@@ -127,7 +127,7 @@ protected:
 class AppExport ConstantExpression : public NumberExpression {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 public:
-    ConstantExpression(const App::DocumentObject *_owner = nullptr,
+    explicit ConstantExpression(const App::DocumentObject *_owner = nullptr,
             const char *_name = "",
             const Base::Quantity &_quantity = Base::Quantity());
 
@@ -170,7 +170,7 @@ public:
         NEG,
         POS
     };
-    OperatorExpression(const App::DocumentObject *_owner = nullptr, Expression * _left = nullptr, Operator _op = NONE, Expression * _right = nullptr);
+    explicit OperatorExpression(const App::DocumentObject *_owner = nullptr, Expression * _left = nullptr, Operator _op = NONE, Expression * _right = nullptr);
 
     ~OperatorExpression() override;
 
@@ -209,7 +209,7 @@ protected:
 class AppExport ConditionalExpression : public Expression {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 public:
-    ConditionalExpression(const App::DocumentObject *_owner = nullptr, Expression * _condition = nullptr,Expression * _trueExpr = nullptr,  Expression * _falseExpr = nullptr);
+    explicit ConditionalExpression(const App::DocumentObject *_owner = nullptr, Expression * _condition = nullptr,Expression * _trueExpr = nullptr,  Expression * _falseExpr = nullptr);
 
     ~ConditionalExpression() override;
 
@@ -290,7 +290,7 @@ public:
         LAST,
     };
 
-    FunctionExpression(const App::DocumentObject *_owner = nullptr, Function _f = NONE,
+    explicit FunctionExpression(const App::DocumentObject *_owner = nullptr, Function _f = NONE,
             std::string &&name = std::string(), std::vector<Expression *> _args = std::vector<Expression*>());
 
     ~FunctionExpression() override;
@@ -327,7 +327,7 @@ protected:
 class AppExport VariableExpression : public UnitExpression {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 public:
-    VariableExpression(const App::DocumentObject *_owner = nullptr, const ObjectIdentifier& _var = ObjectIdentifier());
+    explicit VariableExpression(const App::DocumentObject *_owner = nullptr, const ObjectIdentifier& _var = ObjectIdentifier());
 
     ~VariableExpression() override;
 
@@ -375,7 +375,7 @@ class AppExport PyObjectExpression : public Expression {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 
 public:
-    PyObjectExpression(const App::DocumentObject *_owner=nullptr, PyObject *pyobj=nullptr, bool owned=false)
+    explicit PyObjectExpression(const App::DocumentObject *_owner=nullptr, PyObject *pyobj=nullptr, bool owned=false)
         :Expression(_owner)
     {
         setPyValue(pyobj,owned);
@@ -404,7 +404,7 @@ protected:
 class AppExport StringExpression : public Expression {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 public:
-    StringExpression(const App::DocumentObject *_owner = nullptr, const std::string & _text = std::string());
+    explicit StringExpression(const App::DocumentObject *_owner = nullptr, const std::string & _text = std::string());
     ~StringExpression() override;
 
     Expression * simplify() const override;
@@ -424,7 +424,7 @@ private:
 class AppExport RangeExpression : public App::Expression {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 public:
-    RangeExpression(const App::DocumentObject * _owner = nullptr, const std::string & begin = std::string(), const std::string & end = std::string());
+    explicit RangeExpression(const App::DocumentObject * _owner = nullptr, const std::string & begin = std::string(), const std::string & end = std::string());
 
     ~RangeExpression() override = default;
 
@@ -460,7 +460,7 @@ AppExport std::vector<std::tuple<int, int, std::string> > tokenize(const std::st
 /// Convenient class to mark begin of importing
 class AppExport ExpressionImporter {
 public:
-    ExpressionImporter(Base::XMLReader &reader);
+    explicit ExpressionImporter(Base::XMLReader &reader);
     ~ExpressionImporter();
     static Base::XMLReader *reader();
 };
diff --git a/src/App/ExpressionVisitors.h b/src/App/ExpressionVisitors.h
index 14e91c9af1..3efcf2e4df 100644
--- a/src/App/ExpressionVisitors.h
+++ b/src/App/ExpressionVisitors.h
@@ -34,11 +34,13 @@ namespace App {
 
 template<class P> class RenameObjectIdentifierExpressionVisitor : public ExpressionModifier<P> {
 public:
-    RenameObjectIdentifierExpressionVisitor(P & _prop,
-                                            const std::map<ObjectIdentifier, ObjectIdentifier> &_paths, const ObjectIdentifier & _owner)
-        : ExpressionModifier<P>(_prop)
-        , paths(_paths)
-        , owner(_owner)
+    RenameObjectIdentifierExpressionVisitor(
+        P &_prop,
+        const std::map<ObjectIdentifier, ObjectIdentifier> &_paths,
+        const ObjectIdentifier &_owner )
+        : ExpressionModifier<P>( _prop ),
+          paths( _paths ),
+          owner( _owner )
     {
     }
 
@@ -46,7 +48,6 @@ public:
         this->renameObjectIdentifier(node,paths,owner);
     }
 
-
 private:
    const std::map<ObjectIdentifier, ObjectIdentifier> &paths; /**< Map with current and new object identifiers */
    const ObjectIdentifier owner;                              /**< Owner of expression */
@@ -55,7 +56,7 @@ private:
 template<class P> class UpdateElementReferenceExpressionVisitor : public ExpressionModifier<P> {
 public:
 
-    UpdateElementReferenceExpressionVisitor(P & _prop, App::DocumentObject *feature=nullptr, bool reverse=false)
+    explicit UpdateElementReferenceExpressionVisitor(P & _prop, App::DocumentObject *feature=nullptr, bool reverse=false)
         : ExpressionModifier<P>(_prop),feature(feature),reverse(reverse)
     {
     }
@@ -76,7 +77,7 @@ private:
 class RelabelDocumentExpressionVisitor : public ExpressionVisitor {
 public:
 
-    RelabelDocumentExpressionVisitor(const App::Document &doc)
+    explicit RelabelDocumentExpressionVisitor(const App::Document &doc)
          : doc(doc)
     {
     }
diff --git a/src/App/FeaturePython.h b/src/App/FeaturePython.h
index afe63ca667..93261bc6e4 100644
--- a/src/App/FeaturePython.h
+++ b/src/App/FeaturePython.h
@@ -44,7 +44,7 @@ public:
         Rejected = 2  // handled and rejected
     };
 
-    FeaturePythonImp(App::DocumentObject*);
+    explicit FeaturePythonImp(App::DocumentObject*);
     ~FeaturePythonImp();
 
     bool execute();
diff --git a/src/App/FeaturePythonPyImp.h b/src/App/FeaturePythonPyImp.h
index a31f8095fe..4e2bd58a15 100644
--- a/src/App/FeaturePythonPyImp.h
+++ b/src/App/FeaturePythonPyImp.h
@@ -88,7 +88,7 @@ public:
     static PyTypeObject   Type;
 
 public:
-    FeaturePythonPyT(Base::BaseClass *pcObject, PyTypeObject *T = &Type);
+    explicit FeaturePythonPyT(Base::BaseClass *pcObject, PyTypeObject *T = &Type);
     virtual ~FeaturePythonPyT();
 
     /** @name callbacks and implementers for the python object methods */
diff --git a/src/App/Material.h b/src/App/Material.h
index 43fe4122de..4179015ee6 100644
--- a/src/App/Material.h
+++ b/src/App/Material.h
@@ -50,7 +50,7 @@ public:
      * Does basically the same as the constructor above unless that (R,G,B,A) is
      * encoded as an unsigned int.
      */
-    Color(uint32_t rgba)
+    explicit Color(uint32_t rgba)
     { setPackedValue( rgba ); }
     /** Copy constructor. */
     Color(const Color& c)
@@ -222,9 +222,9 @@ public:
     /** Defines the colors and shininess for the material \a MatName. If \a MatName isn't defined then USER_DEFINED is
      * set and the user must define the colors itself.
      */
-    Material(const char* MatName);
+    explicit Material(const char* MatName);
     /** Does basically the same as the constructor above unless that it accepts a MaterialType as argument. */
-    Material(const MaterialType MatType);
+    explicit Material(const MaterialType MatType);
     //@}
     ~Material();
 
diff --git a/src/App/MergeDocuments.h b/src/App/MergeDocuments.h
index 2f8568e98a..14e1ceca35 100644
--- a/src/App/MergeDocuments.h
+++ b/src/App/MergeDocuments.h
@@ -37,7 +37,7 @@ class DocumentObject;
 class AppExport MergeDocuments : public Base::Persistence
 {
 public:
-    MergeDocuments(App::Document* doc);
+    explicit MergeDocuments(App::Document* doc);
     ~MergeDocuments() override;
     bool isVerbose() const { return verbose; }
     void setVerbose(bool on) { verbose = on; }
diff --git a/src/App/Metadata.h b/src/App/Metadata.h
index 968d91b51d..d5159583c8 100644
--- a/src/App/Metadata.h
+++ b/src/App/Metadata.h
@@ -94,7 +94,7 @@ namespace App {
          */
         struct AppExport Version {
             Version();
-            Version(int major, int minor = 0, int patch = 0, const std::string& suffix = std::string());
+            explicit Version(int major, int minor = 0, int patch = 0, const std::string& suffix = std::string());
             explicit Version(const std::string& semanticString);
 
             int major;
diff --git a/src/App/ObjectIdentifier.cpp b/src/App/ObjectIdentifier.cpp
index 7469c8a824..48fe555853 100644
--- a/src/App/ObjectIdentifier.cpp
+++ b/src/App/ObjectIdentifier.cpp
@@ -856,7 +856,7 @@ App::DocumentObject * ObjectIdentifier::getDocumentObject(const App::Document *
         if (strcmp((*j)->Label.getValue(), static_cast<const char*>(name)) == 0) {
             // Found object with matching label
             if (objectByLabel)  {
-                FC_WARN("duplicate object label " << doc->getName() << '#' << name);
+                FC_WARN("duplicate object label " << doc->getName() << '#' << static_cast<const char*>(name));
                 return nullptr;
             }
             objectByLabel = *j;
@@ -935,13 +935,12 @@ void ObjectIdentifier::resolve(ResolveResults &results) const
         if (!results.resolvedDocumentObject)
             return;
 
-        if (!components.empty()) {
-            results.propertyName = components[0].name.getString();
-            results.propertyIndex = 0;
-            results.getProperty(*this);
-        }
-        else
+        if (components.empty())
             return;
+
+        results.propertyName = components[ 0 ].name.getString();
+        results.propertyIndex = 0;
+        results.getProperty( *this );
     }
     else {
         /* Document object name not specified, resolve from path */
@@ -966,8 +965,10 @@ void ObjectIdentifier::resolve(ResolveResults &results) const
             /* Possible to resolve component to a document object? */
             if (results.resolvedDocumentObject) {
                 /* Yes */
-                results.resolvedDocumentObjectName = String(
-                        components[0].name, false, results.flags.test(ResolveByIdentifier));
+                results.resolvedDocumentObjectName = String {
+                        components[0].name.getString(),
+                        false,
+                        results.flags.test(ResolveByIdentifier)};
                 results.propertyName = components[1].name.getString();
                 results.propertyIndex = 1;
                 results.getProperty(*this);
@@ -976,7 +977,10 @@ void ObjectIdentifier::resolve(ResolveResults &results) const
                     // interpret the first component as the property name.
                     DocumentObject *sobj = nullptr;
                     results.resolvedProperty = resolveProperty(
-                            owner,components[0].name,sobj,results.propertyType);
+                            owner,
+                            components[0].name.toString().c_str(),
+                            sobj,
+                            results.propertyType);
                     if(results.resolvedProperty) {
                         results.propertyName = components[0].name.getString();
                         results.resolvedDocument = owner->getDocument();
@@ -1018,7 +1022,7 @@ Document * ObjectIdentifier::getDocument(String name, bool *ambiguous) const
     App::Document * docById = nullptr;
 
     if(!name.isRealString()) {
-        docById = App::GetApplication().getDocument(name);
+        docById = App::GetApplication().getDocument(name.toString().c_str());
         if (name.isForceIdentifier())
             return docById;
     }
@@ -1267,7 +1271,7 @@ Property *ObjectIdentifier::resolveProperty(const App::DocumentObject *obj,
         const char *propertyName, App::DocumentObject *&sobj, int &ptype) const
 {
     if(obj && !subObjectName.getString().empty()) {
-        sobj = obj->getSubObject(subObjectName);
+        sobj = obj->getSubObject(subObjectName.toString().c_str());
         obj = sobj;
     }
     if(!obj)
diff --git a/src/App/ObjectIdentifier.h b/src/App/ObjectIdentifier.h
index 947c0799d1..133728e909 100644
--- a/src/App/ObjectIdentifier.h
+++ b/src/App/ObjectIdentifier.h
@@ -72,7 +72,7 @@ public:
 
     class AppExport DocumentMapper {
     public:
-        DocumentMapper(const std::map<std::string,std::string> &);
+        explicit DocumentMapper(const std::map<std::string,std::string> &);
         ~DocumentMapper();
     };
 
@@ -81,14 +81,21 @@ public:
 
     public:
 
-        // Constructor
-        String(const std::string & s = "", bool _isRealString = false, bool _forceIdentifier = false)
-            : str(s), isString(_isRealString), forceIdentifier(_forceIdentifier)
-        { }
+        String(const std::string &s = "",
+               bool _isRealString = false,
+               bool _forceIdentifier = false)
+            : str(s),
+            isString(_isRealString),
+            forceIdentifier(_forceIdentifier)
+        {}//explicit bombs
 
-        String(std::string &&s, bool _isRealString = false, bool _forceIdentifier = false)
-            : str(std::move(s)), isString(_isRealString), forceIdentifier(_forceIdentifier)
-        { }
+        explicit String(std::string &&s,
+               bool _isRealString = false,
+               bool _forceIdentifier = false)
+            : str(std::move(s)),
+            isString(_isRealString),
+            forceIdentifier(_forceIdentifier)
+        {}
 
         FC_DEFAULT_CTORS(String) {
             str = std::move(other.str);
@@ -112,9 +119,9 @@ public:
 
         // Operators
 
-        operator std::string() const { return str; }
+        explicit operator std::string() const { return str; }
 
-        operator const char *() const { return str.c_str(); }
+        explicit operator const char *() const { return str.c_str(); }
 
         bool operator==(const String & other) const { return str == other.str; }
 
@@ -166,9 +173,9 @@ public:
         }
 
         Component(const String &_name = String(), typeEnum _type=SIMPLE,
-                int begin=INT_MAX, int end=INT_MAX, int step=1);
+                int begin=INT_MAX, int end=INT_MAX, int step=1);//explicit bombs
         Component(String &&_name, typeEnum _type=SIMPLE,
-                int begin=INT_MAX, int end=INT_MAX, int step=1);
+                int begin=INT_MAX, int end=INT_MAX, int step=1);//explicit bombs
 
         static Component SimpleComponent(const char * _component);
 
@@ -234,6 +241,9 @@ public:
     static Component SimpleComponent(String &&_component)
         {return Component::SimpleComponent(std::move(_component));}
 
+   static Component SimpleComponent(const std::string _component)
+        {return Component::SimpleComponent(_component.c_str());}
+
     static Component ArrayComponent(int _index)
         {return Component::ArrayComponent(_index); }
 
@@ -246,12 +256,12 @@ public:
     static Component MapComponent(String &&_key)
         {return Component::MapComponent(_key);}
 
-    ObjectIdentifier(const App::PropertyContainer * _owner = nullptr,
+    explicit ObjectIdentifier(const App::PropertyContainer * _owner = nullptr,
             const std::string & property = std::string(), int index=INT_MAX);
 
     ObjectIdentifier(const App::PropertyContainer * _owner, bool localProperty);
 
-    ObjectIdentifier(const App::Property & prop, int index=INT_MAX);
+    ObjectIdentifier(const App::Property & prop, int index=INT_MAX);//explicit bombs
 
     FC_DEFAULT_CTORS(ObjectIdentifier) {
         owner = other.owner;
@@ -436,7 +446,7 @@ protected:
 
     struct ResolveResults {
 
-        ResolveResults(const ObjectIdentifier & oi);
+        explicit ResolveResults(const ObjectIdentifier & oi);
 
         int propertyIndex;
         App::Document * resolvedDocument;
diff --git a/src/App/Origin.h b/src/App/Origin.h
index 2146a3ba3b..8deabce0b7 100644
--- a/src/App/Origin.h
+++ b/src/App/Origin.h
@@ -137,7 +137,7 @@ private:
     class OriginExtension : public GeoFeatureGroupExtension {
         Origin* obj;
     public:
-        OriginExtension(Origin* obj);
+        explicit OriginExtension(Origin* obj);
         void initExtension(ExtensionContainer* obj) override;
         bool extensionGetSubObject(DocumentObject *&ret, const char *subname,
                 PyObject **, Base::Matrix4D *, bool, int) const override;
diff --git a/src/App/Path.h b/src/App/Path.h
index b0007fafa4..e354575f76 100644
--- a/src/App/Path.h
+++ b/src/App/Path.h
@@ -40,7 +40,7 @@ protected:
 public:
     /// Constructor
     Path();
-	Path(const std::vector<Base::Persistence *> & PathVector);
+	explicit Path(const std::vector<Base::Persistence *> & PathVector);
 
     virtual ~Path();
 
diff --git a/src/App/Property.cpp b/src/App/Property.cpp
index 4ea7f844f6..edc9b1502e 100644
--- a/src/App/Property.cpp
+++ b/src/App/Property.cpp
@@ -162,7 +162,7 @@ namespace App {
  * active.
  */
 struct PropertyCleaner {
-    PropertyCleaner(Property *p)
+    explicit PropertyCleaner(Property *p)
         : prop(p)
     {
         ++_PropCleanerCounter;
diff --git a/src/App/Property.h b/src/App/Property.h
index f0b494f61b..d10b7994e4 100644
--- a/src/App/Property.h
+++ b/src/App/Property.h
@@ -345,7 +345,7 @@ public:
          *                    hasn't been marked before, and calls its
          *                    aboutToSetValue().
          */
-        AtomicPropertyChange(P & prop, bool markChange=true) : mProp(prop) {
+        explicit AtomicPropertyChange(P & prop, bool markChange=true) : mProp(prop) {
             mProp.signalCounter++;
             if (markChange)
                 aboutToChange();
diff --git a/src/App/PropertyContainer.h b/src/App/PropertyContainer.h
index 40d1c36439..e2ecac07fa 100644
--- a/src/App/PropertyContainer.h
+++ b/src/App/PropertyContainer.h
@@ -73,8 +73,8 @@ struct AppExport PropertyData
   //accepting void*
   struct OffsetBase
   {
-      OffsetBase(const App::PropertyContainer* container) : m_container(container) {}
-      OffsetBase(const App::Extension* container) : m_container(container) {}
+      OffsetBase(const App::PropertyContainer* container) : m_container(container) {}//explicit bombs
+      OffsetBase(const App::Extension* container) : m_container(container) {}//explicit bombs
 
       short int getOffsetTo(const App::Property* prop) const {
             auto *pt = (const char*)prop;
diff --git a/src/App/PropertyExpressionEngine.cpp b/src/App/PropertyExpressionEngine.cpp
index 9fe2d3bfdc..cb7605af42 100644
--- a/src/App/PropertyExpressionEngine.cpp
+++ b/src/App/PropertyExpressionEngine.cpp
@@ -632,7 +632,7 @@ DocumentObjectExecReturn *App::PropertyExpressionEngine::execute(ExecuteOption o
 
     class resetter {
     public:
-        resetter(bool & b) : _b(b) { _b = true; }
+        explicit resetter(bool & b) : _b(b) { _b = true; }
         ~resetter() { _b = false; }
 
     private:
diff --git a/src/App/PropertyExpressionEngine.h b/src/App/PropertyExpressionEngine.h
index 3626bc3971..36ea7c189b 100644
--- a/src/App/PropertyExpressionEngine.h
+++ b/src/App/PropertyExpressionEngine.h
@@ -87,7 +87,7 @@ public:
         std::shared_ptr<App::Expression> expression; /**< The actual expression tree */
         bool busy;
 
-        ExpressionInfo(std::shared_ptr<App::Expression> expression = std::shared_ptr<App::Expression>()) {
+        explicit ExpressionInfo(std::shared_ptr<App::Expression> expression = std::shared_ptr<App::Expression>()) {
             this->expression = expression;
             this->busy = false;
         }
diff --git a/src/App/PropertyLinks.cpp b/src/App/PropertyLinks.cpp
index 699017518f..1bc29a722e 100644
--- a/src/App/PropertyLinks.cpp
+++ b/src/App/PropertyLinks.cpp
@@ -215,7 +215,7 @@ void PropertyLinkBase::_registerElementReference(App::DocumentObject *obj, std::
 
 class StringGuard {
 public:
-    StringGuard(char *c)
+    explicit StringGuard(char *c)
         :c(c)
     {
         v1 = c[0];
diff --git a/src/App/PropertyLinks.h b/src/App/PropertyLinks.h
index 052ba83b2a..133908f4d2 100644
--- a/src/App/PropertyLinks.h
+++ b/src/App/PropertyLinks.h
@@ -1054,7 +1054,7 @@ class AppExport PropertyXLink : public PropertyLinkGlobal
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 
 public:
-    PropertyXLink(bool allowPartial=false, PropertyLinkBase *parent=nullptr);
+    explicit PropertyXLink(bool allowPartial=false, PropertyLinkBase *parent=nullptr);
 
     ~PropertyXLink() override;
 
@@ -1178,7 +1178,7 @@ class AppExport PropertyXLinkSub: public PropertyXLink {
     TYPESYSTEM_HEADER_WITH_OVERRIDE();
 
 public:
-    PropertyXLinkSub(bool allowPartial=false, PropertyLinkBase *parent=nullptr);
+    explicit PropertyXLinkSub(bool allowPartial=false, PropertyLinkBase *parent=nullptr);
 
     ~PropertyXLinkSub() override;
 
diff --git a/src/App/PropertyStandard.h b/src/App/PropertyStandard.h
index ffcea3b306..4a6a9e7b76 100644
--- a/src/App/PropertyStandard.h
+++ b/src/App/PropertyStandard.h
@@ -148,7 +148,7 @@ public:
     PropertyEnumeration();
 
     /// Obvious constructor
-    PropertyEnumeration(const Enumeration &e);
+    explicit PropertyEnumeration(const Enumeration &e);
 
     /// destructor
     ~PropertyEnumeration() override;
diff --git a/src/App/Range.h b/src/App/Range.h
index f40e69557c..89b53d31d9 100644
--- a/src/App/Range.h
+++ b/src/App/Range.h
@@ -49,15 +49,15 @@ struct AppExport CellAddress {
         ShowFull = Absolute | ShowRow | ShowColumn
     };
 
-    CellAddress(int row = -1, int col = -1, bool absRow=false, bool absCol=false) 
+    explicit CellAddress(int row = -1, int col = -1, bool absRow=false, bool absCol=false)
         : _row(row), _col(col), _absRow(absRow), _absCol(absCol) 
     { }
 
-    CellAddress(const char * address) {
+    explicit CellAddress(const char * address) {
         *this = stringToAddress(address);
     }
 
-    CellAddress(const std::string & address) {
+    explicit CellAddress(const std::string & address) {
         *this = stringToAddress(address.c_str());
     }
 
@@ -117,7 +117,7 @@ protected:
 
 class AppExport Range {
 public:
-    Range(const char *range, bool normalize=false);
+    explicit Range(const char *range, bool normalize=false);
 
     Range(int _row_begin, int _col_begin, int _row_end, int _col_end, bool normalize=false);
 
diff --git a/src/App/Transactions.h b/src/App/Transactions.h
index 49bac8df4a..0d0165a55b 100644
--- a/src/App/Transactions.h
+++ b/src/App/Transactions.h
@@ -55,7 +55,7 @@ public:
      * transactions from different document, so that they can be undo/redo
      * together.
      */
-    Transaction(int id = 0);
+    explicit Transaction(int id = 0);
     /// Construction
     ~Transaction() override;
 
@@ -176,7 +176,7 @@ template <class CLASS>
 class TransactionProducer : public Base::AbstractProducer
 {
 public:
-    TransactionProducer (const Base::Type& type)
+    explicit TransactionProducer (const Base::Type& type)
     {
         TransactionFactory::instance().addProducer(type, this);
     }
diff --git a/src/Gui/PreferencePackManager.cpp b/src/Gui/PreferencePackManager.cpp
index 39a73eedf9..7bc3d7a084 100644
--- a/src/Gui/PreferencePackManager.cpp
+++ b/src/Gui/PreferencePackManager.cpp
@@ -386,14 +386,14 @@ void PreferencePackManager::save(const std::string& name, const std::vector<Temp
         metadata = std::make_unique<App::Metadata>();
         metadata->setName("User-Saved PreferencePacks");
         metadata->setDescription("Generated automatically -- edits may be lost when saving new preferencePacks");
-        metadata->setVersion(1);
+        metadata->setVersion(static_cast<App::Meta::Version>(1));
         metadata->addMaintainer(App::Meta::Contact("No Maintainer", "email@freecadweb.org"));
         metadata->addLicense(App::Meta::License("(Unspecified)", "(Unspecified)"));
         metadata->addUrl(App::Meta::Url("https://github.com/FreeCAD/FreeCAD", App::Meta::UrlType::repository));
     }
     App::Metadata newPreferencePackMetadata;
     newPreferencePackMetadata.setName(name);
-    newPreferencePackMetadata.setVersion(1);
+    newPreferencePackMetadata.setVersion(static_cast<App::Meta::Version>(1));
 
     metadata->addContentItem("preferencepack", newPreferencePackMetadata);
     metadata->write(savedPreferencePacksDirectory / "package.xml");
diff --git a/src/Mod/Spreadsheet/App/PropertySheet.cpp b/src/Mod/Spreadsheet/App/PropertySheet.cpp
index 6cd95b2896..0604984bda 100644
--- a/src/Mod/Spreadsheet/App/PropertySheet.cpp
+++ b/src/Mod/Spreadsheet/App/PropertySheet.cpp
@@ -1358,7 +1358,7 @@ void PropertySheet::onRelabeledDocument(const App::Document &doc)
 
 void PropertySheet::renameObjectIdentifiers(const std::map<App::ObjectIdentifier, App::ObjectIdentifier> &paths)
 {
-    RenameObjectIdentifierExpressionVisitor<PropertySheet> v(*this, paths, *this);
+    RenameObjectIdentifierExpressionVisitor<PropertySheet> v {*this, paths, *this};
     for(auto &c : data) {
         c.second->visit(v);
         if(v.changed()) {
diff --git a/src/Mod/TechDraw/Gui/QGIFace.cpp b/src/Mod/TechDraw/Gui/QGIFace.cpp
index 1d999fcb24..af73319adc 100644
--- a/src/Mod/TechDraw/Gui/QGIFace.cpp
+++ b/src/Mod/TechDraw/Gui/QGIFace.cpp
@@ -712,7 +712,7 @@ void QGIFace::getParameters()
 
     hGrp = App::GetApplication().GetUserParameter()
         .GetGroup("BaseApp")->GetGroup("Preferences")->GetGroup("Mod/TechDraw/Colors");
-    App::Color temp = hGrp->GetUnsigned("FaceColor",0xffffffff);
+    App::Color temp {static_cast<uint32_t>(hGrp->GetUnsigned("FaceColor",0xffffffff))};
     setFillColor(temp.asValue<QColor>());
 
     hGrp = App::GetApplication().GetUserParameter()