diff --git a/include/wx/propgrid/editors.h b/include/wx/propgrid/editors.h
index c9c8dddd31..f224386661 100644
--- a/include/wx/propgrid/editors.h
+++ b/include/wx/propgrid/editors.h
@@ -428,7 +428,7 @@ public:
     virtual bool DoShowDialog( wxPropertyGrid* propGrid,
                                wxPGProperty* property ) = 0;
 
-    void SetValue( wxVariant value )
+    void SetValue( const wxVariant& value )
     {
         m_value = value;
     }
diff --git a/include/wx/propgrid/property.h b/include/wx/propgrid/property.h
index 77d8c4b09a..ad3be58c15 100644
--- a/include/wx/propgrid/property.h
+++ b/include/wx/propgrid/property.h
@@ -1736,7 +1736,7 @@ public:
 
     // Helper function (for wxPython bindings and such) for settings protected
     // m_value.
-    void SetValuePlain( wxVariant value )
+    void SetValuePlain( const wxVariant& value )
     {
         m_value = value;
     }
diff --git a/include/wx/propgrid/propgrid.h b/include/wx/propgrid/propgrid.h
index 68f6eab42c..068b08cb3f 100644
--- a/include/wx/propgrid/propgrid.h
+++ b/include/wx/propgrid/propgrid.h
@@ -1299,7 +1299,7 @@ public:
     // changed after the function returns (with true as return value).
     // ValueChangeInEvent() must be used if you wish the application to be
     // able to use wxEVT_PG_CHANGING to potentially veto the given value.
-    void ValueChangeInEvent( wxVariant variant )
+    void ValueChangeInEvent( const wxVariant& variant )
     {
         m_changeInEventValue = variant;
         m_iFlags |= wxPG_FL_VALUE_CHANGE_IN_EVENT;
@@ -2203,7 +2203,7 @@ public:
             m_propertyName = p->GetName();
     }
 
-    void SetPropertyValue( wxVariant value )
+    void SetPropertyValue( const wxVariant& value )
     {
         m_value = value;
     }
diff --git a/include/wx/richtext/richtextsymboldlg.h b/include/wx/richtext/richtextsymboldlg.h
index 40f5621ae4..8c966545df 100644
--- a/include/wx/richtext/richtextsymboldlg.h
+++ b/include/wx/richtext/richtextsymboldlg.h
@@ -137,16 +137,16 @@ public:
 ////@begin wxSymbolPickerDialog member function declarations
 
     wxString GetFontName() const { return m_fontName ; }
-    void SetFontName(wxString value) { m_fontName = value ; }
+    void SetFontName(const wxString& value) { m_fontName = value; }
 
     bool GetFromUnicode() const { return m_fromUnicode ; }
     void SetFromUnicode(bool value) { m_fromUnicode = value ; }
 
     wxString GetNormalTextFontName() const { return m_normalTextFontName ; }
-    void SetNormalTextFontName(wxString value) { m_normalTextFontName = value ; }
+    void SetNormalTextFontName(const wxString& value) { m_normalTextFontName = value; }
 
     wxString GetSymbol() const { return m_symbol ; }
-    void SetSymbol(wxString value) { m_symbol = value ; }
+    void SetSymbol(const wxString& value) { m_symbol = value; }
 
     /// Retrieves bitmap resources
     wxBitmap GetBitmapResource( const wxString& name );
diff --git a/samples/opengl/pyramid/mathstuff.cpp b/samples/opengl/pyramid/mathstuff.cpp
index 754a99663d..17721f8dbc 100644
--- a/samples/opengl/pyramid/mathstuff.cpp
+++ b/samples/opengl/pyramid/mathstuff.cpp
@@ -52,7 +52,7 @@ double MyDistance(const myVec3& v1, const myVec3& v2)
 }
 
 // Angle between two normalized vectors, in radians
-double AngleBetween(myVec3 v1, myVec3 v2)
+double AngleBetween(const myVec3& v1, const myVec3& v2)
 {
     double angle = MyDot(v1, v2);
     // Prevent issues due to numerical precision
diff --git a/samples/opengl/pyramid/mathstuff.h b/samples/opengl/pyramid/mathstuff.h
index 538ea13210..578d206c3f 100644
--- a/samples/opengl/pyramid/mathstuff.h
+++ b/samples/opengl/pyramid/mathstuff.h
@@ -56,7 +56,7 @@ myVec3 MyCross(const myVec3& v1, const myVec3& v2);
 double MyDistance(const myVec3& v1, const myVec3& v2);
 
 // Angle between two normalized vectors, in radians
-double AngleBetween(myVec3 v1, myVec3 v2);
+double AngleBetween(const myVec3& v1, const myVec3& v2);
 
 // Matrix 4x4 by 4x1 multiplication
 myVec4 MyMatMul4x1(const double *m1, const myVec4& v);
diff --git a/samples/opengl/pyramid/oglstuff.cpp b/samples/opengl/pyramid/oglstuff.cpp
index b2d2eafb5b..1f085a7ea8 100644
--- a/samples/opengl/pyramid/oglstuff.cpp
+++ b/samples/opengl/pyramid/oglstuff.cpp
@@ -305,14 +305,14 @@ void myOGLShaders::AddCode(const GLchar* shaString, GLenum shaType)
     m_shaCode.push_back(sv);
 }
 
-void myOGLShaders::AddAttrib(std::string name)
+void myOGLShaders::AddAttrib(const std::string& name)
 {
     shaVars sv = {0, name}; //We will set the location later
     m_shaAttrib.push_back(sv);
     // We don't check the max number of attribute locations (usually 16)
 }
 
-void myOGLShaders::AddUnif(std::string name)
+void myOGLShaders::AddUnif(const std::string& name)
 {
     shaVars sv = {0, name};
     m_shaUnif.push_back(sv);
@@ -333,7 +333,7 @@ void myOGLShaders::SetAttribLocations()
     }
 }
 
-GLuint myOGLShaders::GetAttribLoc(std::string name)
+GLuint myOGLShaders::GetAttribLoc(const std::string& name)
 {
     for (shaVars_v::iterator it = m_shaAttrib.begin(); it != m_shaAttrib.end(); ++it)
     {
@@ -362,7 +362,7 @@ bool myOGLShaders::AskUnifLocations()
     return true;
 }
 
-GLuint myOGLShaders::GetUnifLoc(std::string name)
+GLuint myOGLShaders::GetUnifLoc(const std::string& name)
 {
     for (shaVars_v::iterator it = m_shaUnif.begin(); it != m_shaUnif.end(); ++it)
     {
diff --git a/samples/opengl/pyramid/oglstuff.h b/samples/opengl/pyramid/oglstuff.h
index 010920c2ec..7163c6c750 100644
--- a/samples/opengl/pyramid/oglstuff.h
+++ b/samples/opengl/pyramid/oglstuff.h
@@ -109,10 +109,10 @@ public:
     void CleanUp();
 
     void AddCode(const GLchar* shaString, GLenum shaType);
-    void AddAttrib(std::string name);
-    void AddUnif(std::string name);
-    GLuint GetAttribLoc(std::string name);
-    GLuint GetUnifLoc(std::string name);
+    void AddAttrib(const std::string& name);
+    void AddUnif(const std::string& name);
+    GLuint GetAttribLoc(const std::string& name);
+    GLuint GetUnifLoc(const std::string& name);
     // Disable generic vertex attribute array
     void DisableGenericVAA();