Issue #8013: time.asctime and time.ctime no longer call system asctime

and ctime functions.  The year range for time.asctime is now 1900
through maxint.  The range for time.ctime is the same as for
time.localtime.  The string produced by these functions is longer than
24 characters when year is greater than 9999.

Doc/library/time.rst

@@ -125,7 +125,7 @@ The module defines the following functions and data items:
 .. function:: asctime([t])
 
    Convert a tuple or :class:`struct_time` representing a time as returned by
-   :func:`gmtime` or :func:`localtime` to a 24-character string of the following
+   :func:`gmtime` or :func:`localtime` to a string of the following
    form: ``'Sun Jun 20 23:21:05 1993'``.  If *t* is not provided, the current time
    as returned by :func:`localtime` is used. Locale information is not used by
    :func:`asctime`.

Lib/test/test_time.py

@@ -2,6 +2,7 @@ from test import support
 import time
 import unittest
 import locale
+import sysconfig
 
 class TimeTestCase(unittest.TestCase):
 
@@ -121,34 +122,32 @@ class TimeTestCase(unittest.TestCase):
 
     def test_asctime(self):
         time.asctime(time.gmtime(self.t))
+
+        # Max year is only limited by the size of C int.
+        sizeof_int = sysconfig.get_config_vars('SIZEOF_INT')[0]
+        bigyear = (1 << 8 * sizeof_int - 1) - 1
+        asc = time.asctime((bigyear, 6, 1) + (0,)*6)
+        self.assertEqual(asc[-len(str(bigyear)):], str(bigyear))
+        self.assertRaises(OverflowError, time.asctime, (bigyear + 1,) + (0,)*8)
         self.assertRaises(TypeError, time.asctime, 0)
         self.assertRaises(TypeError, time.asctime, ())
-        # XXX: POSIX-compliant asctime should refuse to convert year > 9999,
-        # but glibc implementation does not.  For now, just check it doesn't
-        # segfault as it did before, and the result contains no newline.
-        try:
-            result = time.asctime((12345, 1, 0, 0, 0, 0, 0, 0, 0))
-        except ValueError:
-            # for POSIX-compliant runtimes
-            pass
-        else:
-            self.assertNotIn('\n', result)
 
     def test_asctime_bounding_check(self):
         self._bounds_checking(time.asctime)
 
     def test_ctime(self):
-        # XXX: POSIX-compliant ctime should refuse to convert year > 9999,
-        # but glibc implementation does not.  For now, just check it doesn't
-        # segfault as it did before, and the result contains no newline.
+        t = time.mktime((1973, 9, 16, 1, 3, 52, 0, 0, -1))
+        self.assertEqual(time.ctime(t), 'Sun Sep 16 01:03:52 1973')
+        t = time.mktime((2000, 1, 1, 0, 0, 0, 0, 0, -1))
+        self.assertEqual(time.ctime(t), 'Sat Jan  1 00:00:00 2000')
         try:
-            result = time.ctime(1e12)
+            bigval = time.mktime((10000, 1, 10) + (0,)*6)
         except ValueError:
-            # for POSIX-compliant runtimes (or 32-bit systems, where time_t
-            # cannot hold timestamps with a five-digit year)
+            # If mktime fails, ctime will fail too.  This may happen
+            # on some platforms.
             pass
         else:
-            self.assertNotIn('\n', result)
+            self.assertEquals(time.ctime(bigval)[-5:], '10000')
 
     @unittest.skipIf(not hasattr(time, "tzset"),
         "time module has no attribute tzset")

Misc/NEWS

@@ -1422,6 +1422,12 @@ Core and Builtins
 Extension Modules
 -----------------
 
+- Issue #8013: time.asctime and time.ctime no longer call system
+  asctime and ctime functions.  The year range for time.asctime is now
+  1900 through maxint.  The range for time.ctime is the same as for
+  time.localtime.  The string produced by these functions is longer
+  than 24 characters when year is greater than 9999.
+
 - Issue #6608: time.asctime is now checking struct tm fields its input
   before passing it to the system asctime.  Patch by MunSic Jeong.
 

Modules/timemodule.c

@@ -599,19 +599,51 @@ time_strptime(PyObject *self, PyObject *args)
     return strptime_result;
 }
 
+
 PyDoc_STRVAR(strptime_doc,
 "strptime(string, format) -> struct_time\n\
 \n\
 Parse a string to a time tuple according to a format specification.\n\
 See the library reference manual for formatting codes (same as strftime()).");
 
+static PyObject *
+_asctime(struct tm *timeptr)
+{
+    /* Inspired by Open Group reference implementation available at
+     * http://pubs.opengroup.org/onlinepubs/009695399/functions/asctime.html */
+    static char wday_name[7][3] = {
+        "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
+    };
+    static char mon_name[12][3] = {
+        "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+        "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
+    };
+    char buf[20]; /* 'Sun Sep 16 01:03:52\0' */
+    int n;
+
+    n = snprintf(buf, sizeof(buf), "%.3s %.3s%3d %.2d:%.2d:%.2d",
+                 wday_name[timeptr->tm_wday],
+                 mon_name[timeptr->tm_mon],
+                 timeptr->tm_mday, timeptr->tm_hour,
+                 timeptr->tm_min, timeptr->tm_sec);
+    /* XXX: since the fields used by snprintf above are validated in checktm,
+     * the following condition should never trigger. We keep the check because
+     * historically fixed size buffer used in asctime was the source of
+     * crashes. */
+    if (n + 1 != sizeof(buf)) {
+        PyErr_SetString(PyExc_ValueError, "unconvertible time");
+        return NULL;
+    }
+
+    return PyUnicode_FromFormat("%s %d", buf, 1900 + timeptr->tm_year);
+}
 
 static PyObject *
 time_asctime(PyObject *self, PyObject *args)
 {
     PyObject *tup = NULL;
     struct tm buf;
-    char *p, *q;
+
     if (!PyArg_UnpackTuple(args, "asctime", 0, 1, &tup))
         return NULL;
     if (tup == NULL) {
@@ -619,17 +651,7 @@ time_asctime(PyObject *self, PyObject *args)
         buf = *localtime(&tt);
     } else if (!gettmarg(tup, &buf) || !checktm(&buf))
         return NULL;
-    p = asctime(&buf);
-    if (p == NULL) {
-        PyErr_SetString(PyExc_ValueError, "unconvertible time");
-        return NULL;
-    }
-    /* Replace a terminating newline by a null byte, normally at position 24.
-     * It can occur later if the year has more than four digits. */
-    for (q = p+24; *q != '\0'; q++)
-        if (*q == '\n')
-            *q = '\0';
-    return PyUnicode_FromString(p);
+    return _asctime(&buf);
 }
 
 PyDoc_STRVAR(asctime_doc,
@@ -644,7 +666,7 @@ time_ctime(PyObject *self, PyObject *args)
 {
     PyObject *ot = NULL;
     time_t tt;
-    char *p, *q;
+    struct tm *timeptr;
 
     if (!PyArg_UnpackTuple(args, "ctime", 0, 1, &ot))
         return NULL;
@@ -658,17 +680,12 @@ time_ctime(PyObject *self, PyObject *args)
         if (tt == (time_t)-1 && PyErr_Occurred())
             return NULL;
     }
-    p = ctime(&tt);
-    if (p == NULL) {
+    timeptr = localtime(&tt);
+    if (timeptr == NULL) {
         PyErr_SetString(PyExc_ValueError, "unconvertible time");
         return NULL;        
     }
-    /* Replace a terminating newline by a null byte, normally at position 24.
-     * It can occur later if the year has more than four digits. */
-    for (q = p+24; *q != '\0'; q++)
-        if (*q == '\n')
-            *q = '\0';
-    return PyUnicode_FromString(p);
+    return _asctime(timeptr);
 }
 
 PyDoc_STRVAR(ctime_doc,