diff --git a/python/core/effects/qgspainteffect.sip b/python/core/effects/qgspainteffect.sip
index a07859607958..f413b5debade 100644
--- a/python/core/effects/qgspainteffect.sip
+++ b/python/core/effects/qgspainteffect.sip
@@ -300,6 +300,9 @@ class QgsDrawSourceEffect : QgsPaintEffect
   public:
 
     QgsDrawSourceEffect();
+%Docstring
+Constructor for QgsDrawSourceEffect
+%End
 
     static QgsPaintEffect *create( const QgsStringMap &map ) /Factory/;
 %Docstring
diff --git a/python/core/qgsdiagramrenderer.sip b/python/core/qgsdiagramrenderer.sip
index b923e3411835..1ff838f0120a 100644
--- a/python/core/qgsdiagramrenderer.sip
+++ b/python/core/qgsdiagramrenderer.sip
@@ -614,7 +614,11 @@ class QgsSingleCategoryDiagramRenderer : QgsDiagramRenderer
 #include "qgsdiagramrenderer.h"
 %End
   public:
+
     QgsSingleCategoryDiagramRenderer();
+%Docstring
+Constructor for QgsSingleCategoryDiagramRenderer
+%End
 
     virtual QgsSingleCategoryDiagramRenderer *clone() const /Factory/;
 
diff --git a/src/core/effects/qgspainteffect.cpp b/src/core/effects/qgspainteffect.cpp
index 1110a1211cf9..bd9426bda0a3 100644
--- a/src/core/effects/qgspainteffect.cpp
+++ b/src/core/effects/qgspainteffect.cpp
@@ -226,11 +226,6 @@ QRectF QgsPaintEffect::imageBoundingRect( const QgsRenderContext &context ) cons
 // QgsDrawSourceEffect
 //
 
-QgsDrawSourceEffect::QgsDrawSourceEffect()
-  : QgsPaintEffect()
-{
-}
-
 QgsPaintEffect *QgsDrawSourceEffect::create( const QgsStringMap &map )
 {
   QgsDrawSourceEffect *effect = new QgsDrawSourceEffect();
diff --git a/src/core/effects/qgspainteffect.h b/src/core/effects/qgspainteffect.h
index bf6d62279fad..eada8923de52 100644
--- a/src/core/effects/qgspainteffect.h
+++ b/src/core/effects/qgspainteffect.h
@@ -326,7 +326,8 @@ class CORE_EXPORT QgsDrawSourceEffect : public QgsPaintEffect
 {
   public:
 
-    QgsDrawSourceEffect();
+    //! Constructor for QgsDrawSourceEffect
+    QgsDrawSourceEffect() = default;
 
     /**
      * Creates a new QgsDrawSource effect from a properties string map.
diff --git a/src/core/layout/qgslayoutundostack.cpp b/src/core/layout/qgslayoutundostack.cpp
index f78efa79c9ca..02fe507007cb 100644
--- a/src/core/layout/qgslayoutundostack.cpp
+++ b/src/core/layout/qgslayoutundostack.cpp
@@ -21,8 +21,7 @@
 #include <QUndoStack>
 
 QgsLayoutUndoStack::QgsLayoutUndoStack( QgsLayout *layout )
-  : QObject()
-  , mLayout( layout )
+  : mLayout( layout )
   , mUndoStack( new QUndoStack( layout ) )
 {
   connect( mUndoStack.get(), &QUndoStack::indexChanged, this, &QgsLayoutUndoStack::indexChanged );
@@ -75,7 +74,6 @@ void QgsLayoutUndoStack::cancelCommand()
 QUndoStack *QgsLayoutUndoStack::stack()
 {
   return mUndoStack.get();
-
 }
 
 void QgsLayoutUndoStack::notifyUndoRedoOccurred( QgsLayoutItem *item )
diff --git a/src/core/qgscolorscheme.cpp b/src/core/qgscolorscheme.cpp
index 404991d9ed31..f73990927b37 100644
--- a/src/core/qgscolorscheme.cpp
+++ b/src/core/qgscolorscheme.cpp
@@ -287,8 +287,7 @@ bool QgsGplColorScheme::setColors( const QgsNamedColorList &colors, const QStrin
 //
 
 QgsUserColorScheme::QgsUserColorScheme( const QString &filename )
-  : QgsGplColorScheme()
-  , mFilename( filename )
+  : mFilename( filename )
 {
   QFile sourceFile( gplFilePath() );
 
diff --git a/src/core/qgsdiagramrenderer.cpp b/src/core/qgsdiagramrenderer.cpp
index a804e9316ce1..f97cfba5e10d 100644
--- a/src/core/qgsdiagramrenderer.cpp
+++ b/src/core/qgsdiagramrenderer.cpp
@@ -539,10 +539,6 @@ void QgsDiagramRenderer::_writeXml( QDomElement &rendererElem, QDomDocument &doc
   rendererElem.setAttribute( QStringLiteral( "attributeLegend" ), mShowAttributeLegend );
 }
 
-QgsSingleCategoryDiagramRenderer::QgsSingleCategoryDiagramRenderer(): QgsDiagramRenderer()
-{
-}
-
 QgsSingleCategoryDiagramRenderer *QgsSingleCategoryDiagramRenderer::clone() const
 {
   return new QgsSingleCategoryDiagramRenderer( *this );
@@ -589,7 +585,6 @@ void QgsSingleCategoryDiagramRenderer::writeXml( QDomElement &layerElem, QDomDoc
 
 
 QgsLinearlyInterpolatedDiagramRenderer::QgsLinearlyInterpolatedDiagramRenderer()
-  : QgsDiagramRenderer()
 {
   mInterpolationSettings.classificationAttributeIsExpression = false;
 }
diff --git a/src/core/qgsdiagramrenderer.h b/src/core/qgsdiagramrenderer.h
index c806168303e6..d9a65f472acb 100644
--- a/src/core/qgsdiagramrenderer.h
+++ b/src/core/qgsdiagramrenderer.h
@@ -646,7 +646,9 @@ class CORE_EXPORT QgsDiagramRenderer
 class CORE_EXPORT QgsSingleCategoryDiagramRenderer : public QgsDiagramRenderer
 {
   public:
-    QgsSingleCategoryDiagramRenderer();
+
+    //! Constructor for QgsSingleCategoryDiagramRenderer
+    QgsSingleCategoryDiagramRenderer() = default;
 
     QgsSingleCategoryDiagramRenderer *clone() const override SIP_FACTORY;
 
diff --git a/src/core/qgsmultirenderchecker.cpp b/src/core/qgsmultirenderchecker.cpp
index ae5d18a7e91a..a8d8f24a8f24 100644
--- a/src/core/qgsmultirenderchecker.cpp
+++ b/src/core/qgsmultirenderchecker.cpp
@@ -108,8 +108,7 @@ QString QgsMultiRenderChecker::controlImagePath() const
 ///@cond PRIVATE
 
 QgsCompositionChecker::QgsCompositionChecker( const QString &testName, QgsComposition *composition )
-  : QgsMultiRenderChecker()
-  , mTestName( testName )
+  : mTestName( testName )
   , mComposition( composition )
   , mSize( 1122, 794 )
   , mDotsPerMeter( 96 / 25.4 * 1000 )
@@ -178,8 +177,7 @@ bool QgsCompositionChecker::testComposition( QString &checkedReport, int page, i
 //
 
 QgsLayoutChecker::QgsLayoutChecker( const QString &testName, QgsLayout *layout )
-  : QgsMultiRenderChecker()
-  , mTestName( testName )
+  : mTestName( testName )
   , mLayout( layout )
   , mSize( 1122, 794 )
   , mDotsPerMeter( 96 / 25.4 * 1000 )
diff --git a/src/plugins/grass/qgsgrassmapcalc.cpp b/src/plugins/grass/qgsgrassmapcalc.cpp
index 181031bd2b52..0333cc9d158f 100644
--- a/src/plugins/grass/qgsgrassmapcalc.cpp
+++ b/src/plugins/grass/qgsgrassmapcalc.cpp
@@ -1384,7 +1384,6 @@ void QgsGrassMapcalc::clear()
 /**************************** OBJECT ************************/
 QgsGrassMapcalcObject::QgsGrassMapcalcObject( int type )
   : QGraphicsRectItem( -1000, -1000, 50, 20, 0 )
-  , QgsGrassMapcalcItem()
   , mType( type )
   , mRound( 0. )
   , mCenter( -1000, -1000 )
@@ -1794,10 +1793,7 @@ QString QgsGrassMapcalcObject::expression()
 
 /************************* CONNECTOR **********************************/
 QgsGrassMapcalcConnector::QgsGrassMapcalcConnector( QGraphicsScene *canvas )
-  : QgsGrassMapcalcItem()
-  , mSelectedEnd( -1 )
 {
-
   canvas->addItem( this );
 
   QGraphicsLineItem::setZValue( 10 );
diff --git a/src/plugins/grass/qgsgrassmapcalc.h b/src/plugins/grass/qgsgrassmapcalc.h
index 06c0e99616e3..1995964685c4 100644
--- a/src/plugins/grass/qgsgrassmapcalc.h
+++ b/src/plugins/grass/qgsgrassmapcalc.h
@@ -504,7 +504,7 @@ class QgsGrassMapcalcConnector: public QGraphicsLineItem, public QgsGrassMapcalc
     std::vector<QPoint> mPoints;
 
     // Selected end, -1 for whole connector
-    int mSelectedEnd;
+    int mSelectedEnd = -1;
 
     // Connected objects
     std::vector<QgsGrassMapcalcObject *> mSocketObjects;