Issue #4705: Fix the -u ("unbuffered binary stdout and stderr") command-line
flag to work properly. Furthermore, when specifying -u, the text stdout
and stderr streams have line-by-line buffering enabled (the default being
to buffer arbitrary chunks of data). Patch by Victor Stinner, test by me.
diff --git a/Modules/main.c b/Modules/main.c
index 3025d09..6de1523 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -292,7 +292,6 @@
 	wchar_t *module = NULL;
 	FILE *fp = stdin;
 	char *p;
-	int unbuffered = 0;
 	int skipfirstline = 0;
 	int stdin_is_interactive = 0;
 	int help = 0;
@@ -374,7 +373,7 @@
 			break;
 
 		case 'u':
-			unbuffered++;
+			Py_UnbufferedStdioFlag = 1;
 			saw_unbuffered_flag = 1;
 			break;
 
@@ -423,7 +422,7 @@
 		Py_InspectFlag = 1;
 	if (!saw_unbuffered_flag &&
 	    (p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0')
-		unbuffered = 1;
+		Py_UnbufferedStdioFlag = 1;
 
 	if (!Py_NoUserSiteDirectory &&
 	    (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0')
@@ -444,7 +443,7 @@
 
 	stdin_is_interactive = Py_FdIsInteractive(stdin, (char *)0);
 
-	if (unbuffered) {
+	if (Py_UnbufferedStdioFlag) {
 #if defined(MS_WINDOWS) || defined(__CYGWIN__)
 		_setmode(fileno(stdin), O_BINARY);
 		_setmode(fileno(stdout), O_BINARY);