Index: Modules/_io/_iomodule.h
===================================================================
--- Modules/_io/_iomodule.h	(revision 76325)
+++ Modules/_io/_iomodule.h	(working copy)
@@ -75,6 +75,14 @@
  * Offset type for positioning.
  */
 
+/* Printing a variable of type off_t (with e.g., PyString_FromFormat)
+   correctly and without producing compiler warnings is surprisingly painful.
+   We identify an integer type whose size matches off_t and then: (1) cast the
+   off_t to that integer type and (2) use the appropriate conversion
+   specification.  The cast is necessary: gcc complains about formatting a
+   long with "%lld" even when both long and long long have the same
+   precision. */
+
 #if defined(MS_WIN64) || defined(MS_WINDOWS)
 
 /* Windows uses long long for offsets */
@@ -83,6 +91,8 @@
 # define PyLong_FromOff_t   PyLong_FromLongLong
 # define PY_OFF_T_MAX       PY_LLONG_MAX
 # define PY_OFF_T_MIN       PY_LLONG_MIN
+# define PY_OFF_T_COMPAT    PY_LONG_LONG /* type compatible with off_t */
+# define PY_PRIdOFF         "lld"        /* format to use for that type */
 
 #else
 
@@ -93,16 +103,22 @@
 # define PyLong_FromOff_t   PyLong_FromSsize_t
 # define PY_OFF_T_MAX       PY_SSIZE_T_MAX
 # define PY_OFF_T_MIN       PY_SSIZE_T_MIN
-#elif (SIZEOF_OFF_T == SIZEOF_LONG_LONG)
+# define PY_OFF_T_COMPAT    Py_ssize_t
+# define PY_PRIdOFF         "zd"
+#elif (HAVE_LONG_LONG && SIZEOF_OFF_T == SIZEOF_LONG_LONG)
 # define PyLong_AsOff_t     PyLong_AsLongLong
 # define PyLong_FromOff_t   PyLong_FromLongLong
 # define PY_OFF_T_MAX       PY_LLONG_MAX
 # define PY_OFF_T_MIN       PY_LLONG_MIN
+# define PY_OFF_T_COMPAT    PY_LONG_LONG
+# define PY_PRIdOFF         "lld"
 #elif (SIZEOF_OFF_T == SIZEOF_LONG)
 # define PyLong_AsOff_t     PyLong_AsLong
 # define PyLong_FromOff_t   PyLong_FromLong
 # define PY_OFF_T_MAX       LONG_MAX
 # define PY_OFF_T_MIN       LONG_MIN
+# define PY_OFF_T_COMPAT    long
+# define PY_PRIdOFF         "ld"
 #else
 # error off_t does not match either size_t, long, or long long!
 #endif
Index: Modules/_io/bufferedio.c
===================================================================
--- Modules/_io/bufferedio.c	(revision 76325)
+++ Modules/_io/bufferedio.c	(working copy)
@@ -582,7 +582,8 @@
     if (n < 0) {
         if (!PyErr_Occurred())
             PyErr_Format(PyExc_IOError,
-                         "Raw stream returned invalid position %zd", n);
+                         "Raw stream returned invalid position %" PY_PRIdOFF,
+			 (PY_OFF_T_COMPAT)n);
         return -1;
     }
     self->abs_pos = n;
@@ -614,7 +615,8 @@
     if (n < 0) {
         if (!PyErr_Occurred())
             PyErr_Format(PyExc_IOError,
-                         "Raw stream returned invalid position %zd", n);
+                         "Raw stream returned invalid position %" PY_PRIdOFF,
+			 (PY_OFF_T_COMPAT)n);
         return -1;
     }
     self->abs_pos = n;