Fix PR_ImplodeTime for Linux x64.

This fixes the following error when building for x64 targets:

base/third_party/nspr/prtime.cc: In function 'PRTime PR_ImplodeTime(const 
PRExplodedTime*)':
base/third_party/nspr/prtime.cc:173: error: integer overflow in expression
base/third_party/nspr/prtime.cc:176: error: integer overflow in expression

PRTime is long long (8 bytes) on ia32, and long (8 bytes) on x64.  On ia32,
LONG_MAX (4 bytes) converted to microseconds fits in the PRTime type, but
on x64 LONG_MAX is 8 bytes and so overflows the PRTime type on conversion.

Avoid these issues by only returning INT_MAX.  On ia32 this is the correct
value, and does not change behaviour.  On x64 the call to timegm() will always
succeed due to the increased range of time_t, so the error condition of -1
should never be reached.

Fix a bug in the conditional expression for 1 second before epoch.

Patch by Joel Stanley

Original review URL: http://codereview.chromium.org/160511

R=dean,wtc
BUG=18231
TEST=new unit test
Review URL: http://codereview.chromium.org/164366

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@23186 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 17 insertions, 6 deletions

diff --git a/base/pr_time_unittest.cc b/base/pr_time_unittest.cc
index 416094c..6dda299 100644
--- a/base/pr_time_unittest.cc
+++ b/base/pr_time_unittest.cc
@@ -205,6 +205,17 @@ TEST_F(PRTimeTest, ParseTimeTestEpochNeg1) {
   EXPECT_EQ(-1, parsed_time.ToTimeT());
 }
 
+// If time_t is 32 bits, a date after year 2038 will overflow time_t and
+// cause timegm() to return -1.  The parsed time should not be 1 second
+// before epoch.
+TEST_F(PRTimeTest, ParseTimeTestEpochNotNeg1) {
+  Time parsed_time;
+
+  EXPECT_EQ(true, Time::FromString(L"Wed Dec 31 23:59:59 GMT 2100",
+                                   &parsed_time));
+  EXPECT_NE(-1, parsed_time.ToTimeT());
+}
+
 TEST_F(PRTimeTest, ParseTimeTestEpochNeg2) {
   Time parsed_time;
 
diff --git a/base/third_party/nspr/prtime.cc b/base/third_party/nspr/prtime.cc
index d9392a8..c3c271b 100644
--- a/base/third_party/nspr/prtime.cc
+++ b/base/third_party/nspr/prtime.cc
@@ -158,22 +158,22 @@ PR_ImplodeTime(const PRExplodedTime *exploded)
     exp_tm.tm_mon  = exploded->tm_month;
     exp_tm.tm_year = exploded->tm_year - 1900;
 
-    // We assume that time_t is defined as a long.
     time_t absolute_time = timegm(&exp_tm);
 
     // If timegm returned -1.  Since we don't pass it a time zone, the only
     // valid case of returning -1 is 1 second before Epoch (Dec 31, 1969).
     if (absolute_time == -1 &&
-        exploded->tm_year != 1969 && exploded->tm_month != 11 &&
-        exploded->tm_mday != 31 && exploded->tm_hour != 23 &&
-        exploded->tm_min != 59 && exploded->tm_sec != 59) {
+        !(exploded->tm_year == 1969 && exploded->tm_month == 11 &&
+        exploded->tm_mday == 31 && exploded->tm_hour == 23 &&
+        exploded->tm_min == 59 && exploded->tm_sec == 59)) {
+      // If we get here, time_t must be 32 bits.
       // Date was possibly too far in the future and would overflow.  Return
       // the most future date possible (year 2038).
       if (exploded->tm_year >= 1970)
-        return static_cast<PRTime>(LONG_MAX) * kSecondsToMicroseconds;
+        return INT_MAX * kSecondsToMicroseconds;
       // Date was possibly too far in the past and would underflow.  Return
       // the most past date possible (year 1901).
-      return static_cast<PRTime>(LONG_MIN) * kSecondsToMicroseconds;
+      return INT_MIN * kSecondsToMicroseconds;
     }
 
     PRTime result = static_cast<PRTime>(absolute_time);