Improve quality of tests for time stamp overflow. For example,

without this patch (encode-time 0 0 0 1 1 1152921504606846976)
returns the obviously-bogus value (-948597 62170) on my RHEL 5.5
x86-64 host.  With it, it reports time overflow.
* deps.mk (editfns.o): Depend on ../lib/intprops.h.
* editfns.c: Include limits.h and intprops.h.
(TIME_T_MIN, TIME_T_MAX): New macros.
(time_overflow): Move earlier, to before first use.
(hi_time, lo_time): New functions, for an accurate test for
out-of-range times.
(Fcurrent_time, Fget_internal_run_time, make_time): Use them.
(Fget_internal_run_time): Don't assume time_t fits in int.
(make_time): Use list2 instead of Fcons twice.
(Fdecode_time): More accurate test for out-of-range times.
(check_tm_member): New function.
(Fencode_time): Use it, to test for out-of-range times.

3 files changed, 92 insertions, 29 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index a0c4941ec1c..b3362b9fbca 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,22 @@
+2011-03-12  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Improve quality of tests for time stamp overflow.  For example,
+	without this patch (encode-time 0 0 0 1 1 1152921504606846976)
+	returns the obviously-bogus value (-948597 62170) on my RHEL 5.5
+	x86-64 host.  With it, it reports time overflow.
+	* deps.mk (editfns.o): Depend on ../lib/intprops.h.
+	* editfns.c: Include limits.h and intprops.h.
+	(TIME_T_MIN, TIME_T_MAX): New macros.
+	(time_overflow): Move earlier, to before first use.
+	(hi_time, lo_time): New functions, for an accurate test for
+	out-of-range times.
+	(Fcurrent_time, Fget_internal_run_time, make_time): Use them.
+	(Fget_internal_run_time): Don't assume time_t fits in int.
+	(make_time): Use list2 instead of Fcons twice.
+	(Fdecode_time): More accurate test for out-of-range times.
+	(check_tm_member): New function.
+	(Fencode_time): Use it, to test for out-of-range times.
+
 2011-03-11  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* editfns.c (time_overflow): New function, refactoring common code.
diff --git a/src/deps.mk b/src/deps.mk
index 2b162b07bb8..fba856c1be3 100644
--- a/src/deps.mk
+++ b/src/deps.mk
@@ -87,7 +87,8 @@ dosfns.o: buffer.h termchar.h termhooks.h frame.h blockinput.h window.h \
    msdos.h dosfns.h dispextern.h charset.h coding.h atimer.h systime.h \
    lisp.h $(config_h)
 editfns.o: editfns.c window.h buffer.h systime.h $(INTERVALS_H) character.h \
-   coding.h frame.h blockinput.h atimer.h ../lib/unistd.h ../lib/strftime.h \
+   coding.h frame.h blockinput.h atimer.h \
+   ../lib/intprops.h ../lib/strftime.h ../lib/unistd.h \
    lisp.h globals.h $(config_h)
 emacs.o: emacs.c commands.h systty.h syssignal.h blockinput.h process.h \
    termhooks.h buffer.h atimer.h systime.h $(INTERVALS_H) lisp.h $(config_h) \
diff --git a/src/editfns.c b/src/editfns.c
index fe8541f718e..4e8ac316a8a 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -45,6 +45,8 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #endif
 
 #include <ctype.h>
+#include <limits.h>
+#include <intprops.h>
 #include <strftime.h>
 
 #include "intervals.h"
@@ -1415,6 +1417,44 @@ DEFUN ("emacs-pid", Femacs_pid, Semacs_pid, 0, 0, 0,
   return make_number (getpid ());
 }
 
+
+
+#ifndef TIME_T_MIN
+# define TIME_T_MIN TYPE_MINIMUM (time_t)
+#endif
+#ifndef TIME_T_MAX
+# define TIME_T_MAX TYPE_MAXIMUM (time_t)
+#endif
+
+/* Report that a time value is out of range for Emacs.  */
+static void
+time_overflow (void)
+{
+  error ("Specified time is not representable");
+}
+
+/* Return the upper part of the time T (everything but the bottom 16 bits),
+   making sure that it is representable.  */
+static EMACS_INT
+hi_time (time_t t)
+{
+  time_t hi = t >> 16;
+  if (((TYPE_SIGNED (time_t)
+	&& TIME_T_MIN >> 16 < MOST_NEGATIVE_FIXNUM
+	&& hi < MOST_NEGATIVE_FIXNUM)
+       || (MOST_POSITIVE_FIXNUM < TIME_T_MAX >> 16
+	   && MOST_POSITIVE_FIXNUM < hi)))
+    time_overflow ();
+  return hi;
+}
+
+/* Return the bottom 16 bits of the time T.  */
+static EMACS_INT
+lo_time (time_t t)
+{
+  return t & ((1 << 16) - 1);
+}
+
 DEFUN ("current-time", Fcurrent_time, Scurrent_time, 0, 0, 0,
        doc: /* Return the current time, as the number of seconds since 1970-01-01 00:00:00.
 The time is returned as a list of three integers.  The first has the
@@ -1429,8 +1469,8 @@ resolution finer than a second.  */)
   EMACS_TIME t;
 
   EMACS_GET_TIME (t);
-  return list3 (make_number ((EMACS_SECS (t) >> 16) & 0xffff),
-		make_number ((EMACS_SECS (t) >> 0)  & 0xffff),
+  return list3 (make_number (hi_time (EMACS_SECS (t))),
+		make_number (lo_time (EMACS_SECS (t))),
 		make_number (EMACS_USECS (t)));
 }
 
@@ -1449,7 +1489,8 @@ on systems that do not provide resolution finer than a second.  */)
 {
 #ifdef HAVE_GETRUSAGE
   struct rusage usage;
-  int secs, usecs;
+  time_t secs;
+  int usecs;
 
   if (getrusage (RUSAGE_SELF, &usage) < 0)
     /* This shouldn't happen.  What action is appropriate?  */
@@ -1464,8 +1505,8 @@ on systems that do not provide resolution finer than a second.  */)
       secs++;
     }
 
-  return list3 (make_number ((secs >> 16) & 0xffff),
-		make_number ((secs >> 0)  & 0xffff),
+  return list3 (make_number (hi_time (secs)),
+		make_number (lo_time (secs)),
 		make_number (usecs));
 #else /* ! HAVE_GETRUSAGE  */
 #ifdef WINDOWSNT
@@ -1477,19 +1518,12 @@ on systems that do not provide resolution finer than a second.  */)
 }
 
 
-/* Report a time value that is out of range for Emacs.  */
-static void
-time_overflow (void)
-{
-  error ("Specified time is not representable");
-}
-
 /* Make a Lisp list that represents the time T.  */
 Lisp_Object
 make_time (time_t t)
 {
-  return Fcons (make_number (t >> 16),
-		Fcons (make_number (t & 0177777), Qnil));
+  return list2 (make_number (hi_time (t)),
+		make_number (lo_time (t)));
 }
 
 /* Decode a Lisp list SPECIFIED_TIME that represents a time.
@@ -1753,7 +1787,9 @@ DOW and ZONE.)  */)
   BLOCK_INPUT;
   decoded_time = localtime (&time_spec);
   UNBLOCK_INPUT;
-  if (! decoded_time)
+  if (! (decoded_time
+	 && MOST_NEGATIVE_FIXNUM - TM_YEAR_BASE <= decoded_time->tm_year
+	 && decoded_time->tm_year <= MOST_POSITIVE_FIXNUM - TM_YEAR_BASE))
     time_overflow ();
   XSETFASTINT (list_args[0], decoded_time->tm_sec);
   XSETFASTINT (list_args[1], decoded_time->tm_min);
@@ -1778,6 +1814,20 @@ DOW and ZONE.)  */)
   return Flist (9, list_args);
 }
 
+/* Return OBJ - OFFSET, checking that OBJ is a valid fixnum and that
+   the result is representable as an int.  Assume OFFSET is small and
+   nonnegative.  */
+static int
+check_tm_member (Lisp_Object obj, int offset)
+{
+  EMACS_INT n;
+  CHECK_NUMBER (obj);
+  n = XINT (obj);
+  if (! (INT_MIN + offset <= n && n - offset <= INT_MAX))
+    time_overflow ();
+  return n - offset;
+}
+
 DEFUN ("encode-time", Fencode_time, Sencode_time, 6, MANY, 0,
        doc: /* Convert SECOND, MINUTE, HOUR, DAY, MONTH, YEAR and ZONE to internal time.
 This is the reverse operation of `decode-time', which see.
@@ -1806,19 +1856,12 @@ usage: (encode-time SECOND MINUTE HOUR DAY MONTH YEAR &optional ZONE)  */)
   struct tm tm;
   Lisp_Object zone = (nargs > 6 ? args[nargs - 1] : Qnil);
 
-  CHECK_NUMBER (args[0]);	/* second */
-  CHECK_NUMBER (args[1]);	/* minute */
-  CHECK_NUMBER (args[2]);	/* hour */
-  CHECK_NUMBER (args[3]);	/* day */
-  CHECK_NUMBER (args[4]);	/* month */
-  CHECK_NUMBER (args[5]);	/* year */
-
-  tm.tm_sec = XINT (args[0]);
-  tm.tm_min = XINT (args[1]);
-  tm.tm_hour = XINT (args[2]);
-  tm.tm_mday = XINT (args[3]);
-  tm.tm_mon = XINT (args[4]) - 1;
-  tm.tm_year = XINT (args[5]) - TM_YEAR_BASE;
+  tm.tm_sec  = check_tm_member (args[0], 0);
+  tm.tm_min  = check_tm_member (args[1], 0);
+  tm.tm_hour = check_tm_member (args[2], 0);
+  tm.tm_mday = check_tm_member (args[3], 0);
+  tm.tm_mon  = check_tm_member (args[4], 1);
+  tm.tm_year = check_tm_member (args[5], TM_YEAR_BASE);
   tm.tm_isdst = -1;
 
   if (CONSP (zone))