workaround for bug in VS 2013 that occurs at Python init time

src/Base/Interpreter.cpp

@@ -485,6 +485,12 @@ const char* InterpreterSingleton::init(int argc,char *argv[])
 #else
         Py_SetProgramName(argv[0]);
 #endif
+        // There is a serious bug in VS from 2010 until 2013 where the file descriptor for stdin, stdout or stderr
+        // returns a valid value for GUI applications (i.e. subsytem = Windows) where it shouldn't.
+        // This causes Python to fail during initialization.
+        // A workaround is to use freopen on stdin, stdout and stderr. See the class Redirection inside main()
+        // https://bugs.python.org/issue17797#msg197474
+        //
         Py_Initialize();
         PyEval_InitThreads();
 #if PY_MAJOR_VERSION >= 3
@@ -505,6 +511,7 @@ const char* InterpreterSingleton::init(int argc,char *argv[])
         this->_global = PyEval_SaveThread();
     }
 #if PY_MAJOR_VERSION >= 3
+    PyGILStateLocker lock;
 #if PY_MINOR_VERSION >= 5
     return Py_EncodeLocale(Py_GetPath(),NULL);
 #else

src/Gui/Application.cpp

@@ -1032,6 +1032,7 @@ bool Application::activateWorkbench(const char* name)
     if (oldWb && oldWb->name() == name)
         return false; // already active
 
+    Base::PyGILStateLocker lock;
     // we check for the currently active workbench and call its 'Deactivated'
     // method, if available
     PyObject* pcOldWorkbench = 0;
@@ -1040,7 +1041,6 @@ bool Application::activateWorkbench(const char* name)
     }
 
     // get the python workbench object from the dictionary
-    Base::PyGILStateLocker lock;
     PyObject* pcWorkbench = 0;
     pcWorkbench = PyDict_GetItemString(_pcWorkbenchDictionary, name);
     // test if the workbench exists

src/Main/MainGui.cpp

@@ -71,6 +71,29 @@ const char sBanner[] = "\xc2\xa9 Juergen Riegel, Werner Mayer, Yorik van Havre 2
 void InitMiniDumpWriter(const std::string&);
 #endif
 
+class Redirection
+{
+public:
+    Redirection(FILE* f)
+        : fi(Base::FileInfo::getTempFileName()), file(f)
+    {
+#ifdef WIN32
+        _wfreopen(fi.toStdWString().c_str(),L"w",file);
+#else
+        freopen(fi.filePath().c_str(),"w",file);
+#endif
+    }
+    ~Redirection()
+    {
+        fclose(file);
+        fi.deleteFile();
+    }
+
+private:
+    Base::FileInfo fi;
+    FILE* file;
+};
+
 #if defined (FC_OS_LINUX) || defined(FC_OS_BSD)
 QString myDecoderFunc(const QByteArray &localFileName)
 {
@@ -133,6 +156,13 @@ int main( int argc, char ** argv )
     }
 #endif
 
+#if PY_MAJOR_VERSION >= 3
+#if defined(_MSC_VER) && _MSC_VER <= 1800
+    // See InterpreterSingleton::init
+    Redirection out(stdout), err(stderr), inp(stdin);
+#endif
+#endif // PY_MAJOR_VERSION
+
     // Name and Version of the Application
     App::Application::Config()["ExeName"] = "FreeCAD";
     App::Application::Config()["ExeVendor"] = "FreeCAD";