base/time_posix.cc: Work around new integer overflow warning.

A new version of Clang warns about the previous version of this code:

  ../../base/time_posix.cc:212:58: warning: overflow in expression; result is 0 with type 'long' [-Winteger-overflow]
        milliseconds = std::numeric_limits<SysTime>::min() *
                                                           ^
  ../../base/time_posix.cc:215:59: warning: overflow in expression; result is -1000 with type 'long' [-Winteger-overflow]
        milliseconds = (std::numeric_limits<SysTime>::max() *
                                                            ^

The warning is legitimate: that code does overflow on LP64 platforms. However,
we will never hit that code on 64-bit platforms, because mktime() will not
overflow when time_t is a 64-bit type. I have added a CHECK about this and
worked around the warning by splitting up the expression.

BUG=24737
R=brettw@chromium.org, thakis@chromium.org

Review URL: https://codereview.chromium.org/15560002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@201735 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 7 insertions, 5 deletions

diff --git a/base/time_posix.cc b/base/time_posix.cc
index 288c6463..3870201 100644
--- a/base/time_posix.cc
+++ b/base/time_posix.cc
@@ -209,12 +209,14 @@ Time Time::FromExploded(bool is_local, const Exploded& exploded) {
     // 999ms to avoid the time being less than any other possible value that
     // this function can return.
     if (exploded.year < 1969) {
-      milliseconds = std::numeric_limits<SysTime>::min() *
-                     kMillisecondsPerSecond;
+      CHECK(sizeof(SysTime) < sizeof(int64)) << "integer overflow";
+      milliseconds = std::numeric_limits<SysTime>::min();
+      milliseconds *= kMillisecondsPerSecond;
     } else {
-      milliseconds = (std::numeric_limits<SysTime>::max() *
-                      kMillisecondsPerSecond) +
-                     kMillisecondsPerSecond - 1;
+      CHECK(sizeof(SysTime) < sizeof(int64)) << "integer overflow";
+      milliseconds = std::numeric_limits<SysTime>::max();
+      milliseconds *= kMillisecondsPerSecond;
+      milliseconds += (kMillisecondsPerSecond - 1);
     }
   } else {
     milliseconds = seconds * kMillisecondsPerSecond + exploded.millisecond;