# reason: fix build with gcc9
# upstream: yes

diff --git src/3rdParty/salomesmesh/inc/Rn.h src/3rdParty/salomesmesh/inc/Rn.h
index 6ec871d93..e92d2275a 100644
--- src/3rdParty/salomesmesh/inc/Rn.h
+++ src/3rdParty/salomesmesh/inc/Rn.h
@@ -180,12 +180,12 @@ class R4: public R3
 {
   friend std::ostream& operator <<(std::ostream& f, const R4 & P )
   { f << P.x << ' ' << P.y << ' ' << P.z << ' ' << P.omega; return f; }
-  friend istream& operator >>(istream& f,  R4 & P)
+  friend std::istream& operator >>(std::istream& f,  R4 & P)
   { f >> P.x >>  P.y >>  P.z >> P.omega ; return f; }
 
   friend std::ostream& operator <<(std::ostream& f, const R4 * P )
   { f << P->x << ' ' << P->y << ' ' << P->z << ' ' << P->omega; return f; }
-  friend istream& operator >>(istream& f,  R4 * P)
+  friend std::istream& operator >>(std::istream& f,  R4 * P)
   { f >> P->x >>  P->y >>  P->z >> P->omega ; return f; }
 
 public:  


diff --git src/Mod/Drawing/App/DrawingExport.cpp src/Mod/Drawing/App/DrawingExport.cpp
index 0c3c23231..550b12c25 100644
--- src/Mod/Drawing/App/DrawingExport.cpp
+++ src/Mod/Drawing/App/DrawingExport.cpp
@@ -81,6 +81,7 @@
 #include <Base/Vector3D.h>
 
 using namespace Drawing;
+using namespace std;
 
 TopoDS_Edge DrawingOutput::asCircle(const BRepAdaptor_Curve& c) const
 {
diff --git src/Mod/Part/App/Geometry2d.cpp src/Mod/Part/App/Geometry2d.cpp
index fb1de909c..979465533 100644
--- src/Mod/Part/App/Geometry2d.cpp
+++ src/Mod/Part/App/Geometry2d.cpp
@@ -83,6 +83,7 @@
 #include <Mod/Part/App/Geom2d/OffsetCurve2dPy.h>
 
 using namespace Part;
+using namespace std;
 
 extern const char* gce_ErrorStatusText(gce_ErrorType et);
 
diff --git src/Mod/Raytracing/App/AppRaytracingPy.cpp src/Mod/Raytracing/App/AppRaytracingPy.cpp
index d48c51c97..1bb2b1b01 100644
--- src/Mod/Raytracing/App/AppRaytracingPy.cpp
+++ src/Mod/Raytracing/App/AppRaytracingPy.cpp
@@ -40,6 +40,8 @@
 #include <Mod/Part/App/TopoShapePy.h>
 #include <App/Application.h>
 
+using namespace std;
+
 
 namespace Raytracing {
 class Module : public Py::ExtensionModule<Module>
diff --git src/Mod/Raytracing/App/LuxFeature.cpp src/Mod/Raytracing/App/LuxFeature.cpp
index 930fe12b7..d1e0a0089 100644
--- src/Mod/Raytracing/App/LuxFeature.cpp
+++ src/Mod/Raytracing/App/LuxFeature.cpp
@@ -38,6 +38,7 @@
 
 
 using namespace Raytracing;
+using namespace std;
 
 PROPERTY_SOURCE(Raytracing::LuxFeature, Raytracing::RaySegment)
 
diff --git src/Mod/Raytracing/App/RayFeature.cpp src/Mod/Raytracing/App/RayFeature.cpp
index cdd2cb6dc..235a98685 100644
--- src/Mod/Raytracing/App/RayFeature.cpp
+++ src/Mod/Raytracing/App/RayFeature.cpp
@@ -36,6 +36,7 @@
 
 
 using namespace Raytracing;
+using namespace std;
 
 PROPERTY_SOURCE(Raytracing::RayFeature, Raytracing::RaySegment)
 
diff --git src/Mod/TechDraw/App/Geometry.cpp src/Mod/TechDraw/App/Geometry.cpp
index c10b63177..d34eeb9bb 100644
--- src/Mod/TechDraw/App/Geometry.cpp
+++ src/Mod/TechDraw/App/Geometry.cpp
@@ -80,6 +80,7 @@
 #include "Geometry.h"
 
 using namespace TechDraw;
+using namespace std;
 
 // Collection of Geometric Features
 Wire::Wire()


--- src/Mod/Part/App/PropertyTopoShape.cpp
+++ src/Mod/Part/App/PropertyTopoShape.cpp
@@ -281,11 +281,11 @@
 static Standard_Boolean  BRepTools_Write(const TopoDS_Shape& Sh, 
                                    const Standard_CString File)
 {
-  ofstream os;
+  std::ofstream os;
 #if OCC_VERSION_HEX >= 0x060800
-  OSD_OpenStream(os, File, ios::out);
+  OSD_OpenStream(os, File, std::ios::out);
 #else
-  os.open(File, ios::out);
+  os.open(File, std::ios::out);
 #endif
   if (!os.rdbuf()->is_open()) return Standard_False;
 

--- src/Mod/Part/App/Geometry.cpp
+++ src/Mod/Part/App/Geometry.cpp
@@ -141,6 +141,7 @@
 #include "Geometry.h"
 
 using namespace Part;
+using namespace std;
 
 
 const char* gce_ErrorStatusText(gce_ErrorType et)