Restore Windows stdio flags after Python initialisation.

samhocevar · samhocevar · commit 14deb53bafd1 · 2018-12-12T18:35:35.000+01:00
Python forcibly sets the file mode for stdin, stdout, and stderr to O_BINARY for several reasons. This causes wprintf() to output UTF-16 instead of going through the proper text conversion. As a result, standard output was all messed up after the module was initialised. The Python developers do not really consider this a bug because they are not familiar with wprintf() (https://bugs.python.org/issue16587). Unfortunately this is what UE4 uses for logging.
diff --git a/Source/UnrealEnginePython/Private/UnrealEnginePython.cpp b/Source/UnrealEnginePython/Private/UnrealEnginePython.cpp
@@ -34,9 +34,14 @@ const char *ue4_module_options = "linux_global_symbols";
 #include "Runtime/Core/Public/Misc/CommandLine.h"
 #include "Runtime/Core/Public/Misc/ConfigCacheIni.h"
 #include "Runtime/Core/Public/GenericPlatform/GenericPlatformFile.h"
+#include "Runtime/Core/Public/GenericPlatform/GenericPlatformMisc.h"
 
 #include "Runtime/Core/Public/HAL/FileManagerGeneric.h"
 
+#if PLATFORM_WINDOWS
+#include <fcntl.h>
+#endif
+
 #if PLATFORM_ANDROID
 #include "Android/AndroidJNI.h"
 #include "Android/AndroidApplication.h"
@@ -447,6 +452,22 @@ void FUnrealEnginePythonModule::StartupModule()
 
 	Py_Initialize();
 
+#if PLATFORM_WINDOWS
+	// Restore stdio state after Py_Initialize set it to O_BINARY, otherwise
+	// everything that the engine will output is going to be encoded in UTF-16.
+	// The behaviour is described here: https://bugs.python.org/issue16587
+	_setmode(fileno(stdin), O_TEXT);
+	_setmode(fileno(stdout), O_TEXT);
+	_setmode(fileno(stderr), O_TEXT);
+
+	// Also restore the user-requested UTF-8 flag if relevant (behaviour copied
+	// from LaunchEngineLoop.cpp).
+	if (FParse::Param(FCommandLine::Get(), TEXT("UTF8Output")))
+	{
+		FPlatformMisc::SetUTF8Output();
+	}
+#endif
+
 	PyEval_InitThreads();
 
 #if WITH_EDITOR
