android: fix base::Time::FromLocalExploded() crash.

base/time/time_posix.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/time/time.h"
 
 #include <stdint.h>
 #include <sys/time.h>
 #include <time.h>
 #if defined(OS_ANDROID)
@@ skipping 196 matching lines @@
   timestruct.tm_mon    = exploded.month - 1;
   timestruct.tm_year   = exploded.year - 1900;
   timestruct.tm_wday   = exploded.day_of_week;  // mktime/timegm ignore this
   timestruct.tm_yday   = 0;     // mktime/timegm ignore this
   timestruct.tm_isdst  = -1;    // attempt to figure it out
 #if !defined(OS_NACL) && !defined(OS_SOLARIS)
   timestruct.tm_gmtoff = 0;     // not a POSIX field, so mktime/timegm ignore
   timestruct.tm_zone   = NULL;  // not a POSIX field, so mktime/timegm ignore
 #endif
 
-  SysTime seconds = SysTimeFromTimeStruct(&timestruct, is_local);
 
   int64 milliseconds;
+  SysTime seconds;
+
+#if defined(OS_ANDROID)

[jar (doing other things), 2013/10/18 02:14:17]

This probably isn't an android only problem.  It really relates to proper use of
mktime.

[digit1, 2013/10/18 08:54:59]

Thanks, I've remove the #if defined(OS_ANDROID) now.

As will all things related to timezones, I hope this won't generate new
interesting "surprises" on the desktop ;-)

+  // Certain exploded dates do not really exist due to daylight saving times,
+  // and this causes mktime() to return implementation-defined values when
+  // tm_isdst is set to -1. On Android, the function will return -1, while the
+  // C libraries of other platforms typically return a liberally chosen value.
+  // Handling this requires the special code below.
+
+  // SysTimeFromTimeStruct() modifies the input structure, save current value.
+  struct tm timestruct0 = timestruct;
+
+  seconds = SysTimeFromTimeStruct(&timestruct, is_local);
+  if (seconds == -1) {
+    // Get the time values with tm_isdst == 0 and 1, then select the closest one
+    // to UTC 00:00:00 that isn't -1.
+    timestruct = timestruct0;
+    timestruct.tm_isdst = 0;
+    int64 seconds_isdst0 = SysTimeFromTimeStruct(&timestruct, is_local);
+
+    timestruct = timestruct0;
+    timestruct.tm_isdst = 1;
+    int64 seconds_isdst1 = SysTimeFromTimeStruct(&timestruct, is_local);
+
+    // seconds_isdst0 or seconds_isdst1 can be -1 for some timezones.
+    // E.g. "CLST" (Chile Summer Time) returns -1 for 'tm_isdt == 1'.
+    if (seconds_isdst0 < 0)
+      seconds = seconds_isdst1;
+    else if (seconds_isdst1 < 0)
+      seconds = seconds_isdst0;
+    else
+      seconds = std::min(seconds_isdst0, seconds_isdst1);
+  }
+#else
+  seconds = SysTimeFromTimeStruct(&timestruct, is_local);
+#endif
+
   // Handle overflow.  Clamping the range to what mktime and timegm might
   // return is the best that can be done here.  It's not ideal, but it's better
   // than failing here or ignoring the overflow case and treating each time
   // overflow as one second prior to the epoch.
   if (seconds == -1 &&
       (exploded.year < 1969 || exploded.year > 1970)) {
     // If exploded.year is 1969 or 1970, take -1 as correct, with the
     // time indicating 1 second prior to the epoch.  (1970 is allowed to handle
     // time zone and DST offsets.)  Otherwise, return the most future or past
     // time representable.  Assumes the time_t epoch is 1970-01-01 00:00:00 UTC.
     //
     // The minimum and maximum representible times that mktime and timegm could
     // return are used here instead of values outside that range to allow for
     // proper round-tripping between exploded and counter-type time
     // representations in the presence of possible truncation to time_t by
     // division and use with other functions that accept time_t.
     //
     // When representing the most distant time in the future, add in an extra
     // 999ms to avoid the time being less than any other possible value that
     // this function can return.
+
+    // On Android, SysTime is int64, special care must be taken to avoid
+    // overflows.
+    const int64 min_seconds = (sizeof(SysTime) < sizeof(int64))
+                                  ? std::numeric_limits<SysTime>::min()
+                                  : std::numeric_limits<int32_t>::min();
+    const int64 max_seconds = (sizeof(SysTime) < sizeof(int64))
+                                  ? std::numeric_limits<SysTime>::max()
+                                  : std::numeric_limits<int32_t>::max();
     if (exploded.year < 1969) {
-      CHECK(sizeof(SysTime) < sizeof(int64)) << "integer overflow";
-      milliseconds = std::numeric_limits<SysTime>::min();
-      milliseconds *= kMillisecondsPerSecond;
+      milliseconds = min_seconds * kMillisecondsPerSecond;
     } else {
-      CHECK(sizeof(SysTime) < sizeof(int64)) << "integer overflow";
-      milliseconds = std::numeric_limits<SysTime>::max();
-      milliseconds *= kMillisecondsPerSecond;
+      milliseconds = max_seconds * kMillisecondsPerSecond;
       milliseconds += (kMillisecondsPerSecond - 1);
     }
   } else {
     milliseconds = seconds * kMillisecondsPerSecond + exploded.millisecond;
   }
 
   // Adjust from Unix (1970) to Windows (1601) epoch.
   return Time((milliseconds * kMicrosecondsPerMillisecond) +
       kWindowsEpochDeltaMicroseconds);
 }
@@ skipping 85 matching lines @@
     result.tv_usec = static_cast<suseconds_t>(Time::kMicrosecondsPerSecond) - 1;
     return result;
   }
   int64 us = us_ - kTimeTToMicrosecondsOffset;
   result.tv_sec = us / Time::kMicrosecondsPerSecond;
   result.tv_usec = us % Time::kMicrosecondsPerSecond;
   return result;
 }
 
 }  // namespace base