[PATCH v3] Y2038: make __mktime_internal compatibles with __time64_t

["Albert ARIBAUD (3ADEV)" <albert dot aribaud at 3adev dot fr>]

From: Paul Eggert <eggert@cs.ucla.edu>

This implies also making its callers 64-bit-time compatible
(these are mktime/localtime and timegm) and providing wrappers
for 32-bit-time userland to call.

This patch was tested by running 'make check' on branch
master then applying this patch and its two predecessors and
running 'make check' again, and checking that both 'make check'
yield identical results. This was done on x86_64-linux-gnu and
i686-linux-gnu.

* include/time.h (__mktime64): Add prototype.
* include/time.h (__localtime64): Likewise.
* include/time.h (fits_in_time_t): New static function.
* time/mktime.c (__mktime64): New function.
* time/timegm.c (__timegm64): Likewise.
* time/mktime.c (mktime) [__TIMESIZE]: New wrapper function.
* time/timegm.c (timegm) [__TIMESIZE]: Likewise.
---
 include/time.h | 33 ++++++++++++++++++----
 time/mktime.c  | 76 +++++++++++++++++++++++++++++++++-----------------
 time/timegm.c  | 21 ++++++++++++--
 3 files changed, 96 insertions(+), 34 deletions(-)

diff --git a/include/time.h b/include/time.h
index 7b435c00c2..76d5707170 100644
--- a/include/time.h
+++ b/include/time.h
@@ -3,6 +3,7 @@
 
 #ifndef _ISOMAC
 # include <bits/types/locale_t.h>
+# include <stdbool.h>
 
 extern __typeof (strftime_l) __strftime_l;
 libc_hidden_proto (__strftime_l)
@@ -16,6 +17,18 @@ libc_hidden_proto (localtime)
 libc_hidden_proto (strftime)
 libc_hidden_proto (strptime)
 
+#if __TIMESIZE == 64
+# define __timegm64 timegm
+# define __mktime64 mktime
+# define __timelocal64 timelocal
+#else
+extern __time64_t __timegm64 (struct tm *__tp) __THROW;
+extern __time64_t __mktime64 (struct tm *__tp) __THROW;
+/* Another name for `__mktime64'.  */
+extern __time64_t __timelocal64 (struct tm *__tp) __THROW;
+#endif
+
+
 extern __typeof (clock_getres) __clock_getres;
 extern __typeof (clock_gettime) __clock_gettime;
 libc_hidden_proto (__clock_gettime)
@@ -49,13 +62,13 @@ extern void __tzset_parse_tz (const char *tz) attribute_hidden;
 extern void __tz_compute (__time64_t timer, struct tm *tm, int use_localtime)
   __THROW attribute_hidden;
 
-/* Subroutine of `mktime'.  Return the `time_t' representation of TP and
-   normalize TP, given that a `struct tm *' maps to a `time_t' as performed
+/* Subroutine of mktime.  Return the __time64_t representation of TP and
+   normalize TP, given that a struct tm * maps to a __time64_t as performed
    by FUNC.  Record next guess for localtime-gmtime offset in *OFFSET.  */
-extern time_t __mktime_internal (struct tm *__tp,
-				 struct tm *(*__func) (const time_t *,
-						       struct tm *),
-				 long int *__offset) attribute_hidden;
+extern __time64_t __mktime_internal (struct tm *__tp,
+				     struct tm *(*__func) (const __time64_t *,
+							   struct tm *),
+				     long int *__offset) attribute_hidden;
 
 /* nis/nis_print.c needs ctime, so even if ctime is not declared here,
    we define __ctime64 as ctime so that nis/nis_print.c can get linked
@@ -141,5 +154,13 @@ extern double __difftime (time_t time1, time_t time0);
    actual clock ID.  */
 #define CLOCK_IDFIELD_SIZE	3
 
+/* Check whether a time64_t value fits in a time_t.  */
+static inline bool
+fits_in_time_t (__time64_t t64)
+{
+  time_t t = t64;
+  return t == t64;
+}
+
 #endif
 #endif
diff --git a/time/mktime.c b/time/mktime.c
index 00f0dec6b4..533e05d6ab 100644
--- a/time/mktime.c
+++ b/time/mktime.c
@@ -51,6 +51,7 @@
 
 #include <time.h>
 
+#include <errno.h>
 #include <limits.h>
 #include <stdbool.h>
 #include <stdlib.h>
@@ -125,11 +126,11 @@ my_tzset (void)
    to be subtracted from each other, and sometimes with an offset
    added to them, without worrying about overflow.
 
-   Much of the code uses long_int to represent time_t values, to
-   lessen the hassle of dealing with platforms where time_t is
-   unsigned, and because long_int should suffice to represent all
-   time_t values that mktime can generate even on platforms where
-   time_t is excessively wide.  */
+   Much of the code uses long_int to represent __time64_t values, to
+   lessen the hassle of dealing with Gnulib-using platforms where
+   __time64_t is time_t and time_t is unsigned, and because long_int
+   should suffice to represent all __time64_t values that mktime can
+   generate even on platforms where __time64_t is excessively wide.  */
 
 #if INT_MAX <= LONG_MAX / 3 / 366 / 24 / 60 / 60
 typedef long int long_int;
@@ -157,16 +158,17 @@ shr (long_int a, int b)
 	  : a / (one << b) - (a % (one << b) < 0));
 }
 
-/* Bounds for the intersection of time_t and long_int.  */
+/* Bounds for the intersection of __time64_t and long_int.  */
 
 static long_int const mktime_min
-  = ((TYPE_SIGNED (time_t) && TYPE_MINIMUM (time_t) < TYPE_MINIMUM (long_int))
-     ? TYPE_MINIMUM (long_int) : TYPE_MINIMUM (time_t));
+  = ((TYPE_SIGNED (__time64_t)
+      && TYPE_MINIMUM (__time64_t) < TYPE_MINIMUM (long_int))
+     ? TYPE_MINIMUM (long_int) : TYPE_MINIMUM (__time64_t));
 static long_int const mktime_max
-  = (TYPE_MAXIMUM (long_int) < TYPE_MAXIMUM (time_t)
-     ? TYPE_MAXIMUM (long_int) : TYPE_MAXIMUM (time_t));
+  = (TYPE_MAXIMUM (long_int) < TYPE_MAXIMUM (__time64_t)
+     ? TYPE_MAXIMUM (long_int) : TYPE_MAXIMUM (__time64_t));
 
-verify (TYPE_IS_INTEGER (time_t));
+verify (TYPE_IS_INTEGER (__time64_t));
 
 #define EPOCH_YEAR 1970
 #define TM_YEAR_BASE 1900
@@ -247,11 +249,11 @@ long_int_avg (long_int a, long_int b)
   return shr (a, 1) + shr (b, 1) + ((a | b) & 1);
 }
 
-/* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC),
+/* Return a __time64_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC),
    assuming that T corresponds to *TP and that no clock adjustments
    occurred between *TP and the desired time.
    Although T and the returned value are of type long_int,
-   they represent time_t values and must be in time_t range.
+   they represent __time64_t values and must be in __time64_t range.
    If TP is null, return a value not equal to T; this avoids false matches.
    YEAR and YDAY must not be so large that multiplying them by three times the
    number of seconds in a year (or day, respectively) would overflow long_int.
@@ -282,22 +284,22 @@ guess_time_tm (long_int year, long_int yday, int hour, int min, int sec,
 }
 
 /* Use CONVERT to convert T to a struct tm value in *TM.  T must be in
-   range for time_t.  Return TM if successful, NULL if T is out of
+   range for __time64_t.  Return TM if successful, NULL if T is out of
    range for CONVERT.  */
 static struct tm *
-convert_time (struct tm *(*convert) (const time_t *, struct tm *),
+convert_time (struct tm *(*convert) (const __time64_t *, struct tm *),
 	      long_int t, struct tm *tm)
 {
-  time_t x = t;
+  __time64_t x = t;
   return convert (&x, tm);
 }
 
 /* Use CONVERT to convert *T to a broken down time in *TP.
    If *T is out of range for conversion, adjust it so that
    it is the nearest in-range value and then convert that.
-   A value is in range if it fits in both time_t and long_int.  */
+   A value is in range if it fits in both __time64_t and long_int.  */
 static struct tm *
-ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
+ranged_convert (struct tm *(*convert) (const __time64_t *, struct tm *),
 		long_int *t, struct tm *tp)
 {
   struct tm *r;
@@ -339,15 +341,15 @@ ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
 }
 
 
-/* Convert *TP to a time_t value, inverting
+/* Convert *TP to a __time64_t value, inverting
    the monotonic and mostly-unit-linear conversion function CONVERT.
    Use *OFFSET to keep track of a guess at the offset of the result,
    compared to what the result would be for UTC without leap seconds.
    If *OFFSET's guess is correct, only one CONVERT call is needed.
    This function is external because it is used also by timegm.c.  */
-time_t
+__time64_t
 __mktime_internal (struct tm *tp,
-		   struct tm *(*convert) (const time_t *, struct tm *),
+		   struct tm *(*convert) (const __time64_t *, struct tm *),
 		   mktime_offset_t *offset)
 {
   long_int t, gt, t0, t1, t2, dt;
@@ -518,9 +520,9 @@ __mktime_internal (struct tm *tp,
 
 #if defined _LIBC || NEED_MKTIME_WORKING || NEED_MKTIME_WINDOWS
 
-/* Convert *TP to a time_t value.  */
-time_t
-mktime (struct tm *tp)
+/* Convert *TP to a __time64_t value.  */
+__time64_t
+__mktime64 (struct tm *tp)
 {
   /* POSIX.1 8.1.1 requires that whenever mktime() is called, the
      time zone names contained in the external variable 'tzname' shall
@@ -529,7 +531,7 @@ mktime (struct tm *tp)
 
 # if defined _LIBC || NEED_MKTIME_WORKING
   static mktime_offset_t localtime_offset;
-  return __mktime_internal (tp, __localtime_r, &localtime_offset);
+  return __mktime_internal (tp, __localtime64_r, &localtime_offset);
 # else
 #  undef mktime
   return mktime (tp);
@@ -537,6 +539,28 @@ mktime (struct tm *tp)
 }
 #endif /* _LIBC || NEED_MKTIME_WORKING || NEED_MKTIME_WINDOWS */
 
+#ifdef weak_alias
+weak_alias (__mktime64, __timelocal64)
+#endif
+
+#ifdef _LIBC
+libc_hidden_def (__mktime64)
+libc_hidden_weak (__timelocal64)
+#endif
+
+#if __TIMESIZE != 64
+
+/* The 32-bit-time wrapper.  */
+time_t
+mktime (struct tm *tp)
+{
+  __time64_t t64 = __mktime64 (tp);
+  if (fits_in_time_t (t64))
+    return t64;
+  __set_errno (EOVERFLOW);
+  return -1;
+}
+
 #ifdef weak_alias
 weak_alias (mktime, timelocal)
 #endif
@@ -545,6 +569,8 @@ weak_alias (mktime, timelocal)
 libc_hidden_def (mktime)
 libc_hidden_weak (timelocal)
 #endif
+
+#endif
 
 #if DEBUG_MKTIME
 
diff --git a/time/timegm.c b/time/timegm.c
index 229fff23c6..e7718ee170 100644
--- a/time/timegm.c
+++ b/time/timegm.c
@@ -24,11 +24,26 @@
 #include <time.h>
 
 #include "mktime-internal.h"
+#include <errno.h>
+
+__time64_t
+__timegm64 (struct tm *tmp)
+{
+  static long int gmtime_offset;
+  tmp->tm_isdst = 0;
+  return __mktime_internal (tmp, __gmtime64_r, &gmtime_offset);
+}
+
+#if __TIMESIZE != 64
 
 time_t
 timegm (struct tm *tmp)
 {
-  static mktime_offset_t gmtime_offset;
-  tmp->tm_isdst = 0;
-  return __mktime_internal (tmp, __gmtime_r, &gmtime_offset);
+  __time64_t t64 = __timegm64 (tmp);
+  if (fits_in_time_t (t64))
+    return t64;
+  __set_errno (EOVERFLOW);
+  return -1;
 }
+
+#endif
-- 
2.17.1