SF bug 563750 (Alex Martelli): posix_tmpfile():

The file returned by tmpfile() has mode w+b, so use that in the call
to PyFile_FromFile().

Bugfix candidate.

Doc/lib/libos.tex

@@ -312,7 +312,7 @@ Availability: \UNIX, Windows.
 \end{funcdesc}
 
 \begin{funcdesc}{tmpfile}{}
-Return a new file object opened in update mode (\samp{w+}).  The file
+Return a new file object opened in update mode (\samp{w+b}).  The file
 has no directory entries associated with it and will be automatically
 deleted once there are no file descriptors for the file.
 Availability: \UNIX, Windows.

Modules/posixmodule.c

@@ -5194,7 +5194,7 @@ posix_tmpfile(PyObject *self, PyObject *args)
     fp = tmpfile();
     if (fp == NULL)
         return posix_error();
-    return PyFile_FromFile(fp, "<tmpfile>", "w+", fclose);
+    return PyFile_FromFile(fp, "<tmpfile>", "w+b", fclose);
 }
 #endif