python#4747: on Windows, starting a module with a non-ascii filename …

…would print a useless "SyntaxError: None"

when the script contains a "# coding:" declaration.

The Python API expects char* to be utf-8 encoded. wcstombs should be avoided here.

Reviewed by Benjamin. Will backport to 3.0

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 3.1 alpha 0
 Core and Builtins
 -----------------
 
+- Issue #4747: When the terminal does not use utf-8, executing a script with
+  non-ascii characters in its name could fail with a "SyntaxError: None" error.
+
 - Issue #4797: IOError.filename was not set when _fileio.FileIO failed to open
   file with `bytes' filename on Windows.
 

Modules/main.c

@@ -600,18 +600,21 @@ Py_Main(int argc, wchar_t **argv)
 		}
 
 		if (sts==-1) {
-			char cfilename[PATH_MAX];
+			PyObject *filenameObj = NULL;
 			char *p_cfilename = "<stdin>";
 			if (filename) {
-				size_t r = wcstombs(cfilename, filename, PATH_MAX);
-				p_cfilename = cfilename;
-				if (r == (size_t)-1 || r >= PATH_MAX)
+				filenameObj = PyUnicode_FromWideChar(
+					filename, wcslen(filename));
+				if (filenameObj != NULL)
+					p_cfilename = _PyUnicode_AsString(filenameObj);
+				else
 					p_cfilename = "<decoding error>";
 			}
 			sts = PyRun_AnyFileExFlags(
 				fp,
 				p_cfilename,
 				filename != NULL, &cf) != 0;
+			Py_XDECREF(filenameObj);
 		}
 
 	}