Silence gcc warnings when trying to print an off_t using "lld", on platforms

where off_t has type long (e.g., 64-bit Linux).

Modules/_io/_iomodule.h

@@ -75,6 +75,14 @@ PyAPI_DATA(PyObject *) PyExc_BlockingIOError;
  * Offset type for positioning.
  */
 
+/* Printing a variable of type off_t 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
+   for printf.  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 */
@@ -84,7 +92,7 @@ typedef PY_LONG_LONG Py_off_t;
 # define PY_OFF_T_MAX       PY_LLONG_MAX
 # define PY_OFF_T_MIN       PY_LLONG_MIN
 # define PY_PRIdOFF         "lld" /* format to use in printf with type off_t */
-
+# define PY_OFF_T_COMPAT    long long /* standard type compatible with off_t */
 #else
 
 /* Other platforms use off_t */
@@ -95,18 +103,21 @@ typedef off_t Py_off_t;
 # define PY_OFF_T_MAX       PY_LLONG_MAX
 # define PY_OFF_T_MIN       PY_LLONG_MIN
 # define PY_PRIdOFF         "lld"
+# define PY_OFF_T_COMPAT    long long
 #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_PRIdOFF         "ld"
+# define PY_OFF_T_COMPAT    long
 #elif (SIZEOF_OFF_T == SIZEOF_SIZE_T)
 # define PyLong_AsOff_t     PyLong_AsSsize_t
 # 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
 # define PY_PRIdOFF         "zd"
+# define PY_OFF_T_COMPAT    Py_ssize_t
 #else
 # error off_t does not match either size_t, long, or long long!
 #endif

Modules/_io/bufferedio.c

@@ -581,7 +581,7 @@ _buffered_raw_tell(buffered *self)
         if (!PyErr_Occurred())
             PyErr_Format(PyExc_IOError,
                          "Raw stream returned invalid position %" PY_PRIdOFF,
-			 n);
+			 (PY_OFF_T_COMPAT)n);
         return -1;
     }
     self->abs_pos = n;
@@ -614,7 +614,7 @@ _buffered_raw_seek(buffered *self, Py_off_t target, int whence)
         if (!PyErr_Occurred())
             PyErr_Format(PyExc_IOError,
                          "Raw stream returned invalid position %" PY_PRIdOFF,
-			 n);
+			 (PY_OFF_T_COMPAT)n);
         return -1;
     }
     self->abs_pos = n;