poll: use GetTickCount64() to avoid wrap-around issues

The value of timeout starts as an int value, and for this reason it
cannot overflow unsigned long long aka ULONGLONG. The unsigned version
of this initial value is available in orig_timeout. The difference
(orig_timeout - elapsed) cannot wrap around because it is protected by
a conditional (as can be seen in the patch text). Hence, the ULONGLONG
difference can only have values that are smaller than the initial
timeout value and truncation to int cannot overflow.

Signed-off-by: Steve Hoelzer <shoelzer@gmail.com>
[j6t: improved both implementation and log message]
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/compat/poll/poll.c b/compat/poll/poll.c
index ad5dcde439d3db239c29cda25d30e6b3a847a861..4459408c7d0ba762b1dd4184a4c970778ba097a5 100644 (file)
--- a/compat/poll/poll.c
+++ b/compat/poll/poll.c
@@ -18,6 +18,9 @@
    You should have received a copy of the GNU General Public License along
    with this program; if not, see <http://www.gnu.org/licenses/>.  */
 
+/* To bump the minimum Windows version to Windows Vista */
+#include "git-compat-util.h"
+
 /* Tell gcc not to warn about the (nfd < 0) tests, below.  */
 #if (__GNUC__ == 4 && 3 <= __GNUC_MINOR__) || 4 < __GNUC__
 # pragma GCC diagnostic ignored "-Wtype-limits"
@@ -449,7 +452,8 @@ poll (struct pollfd *pfd, nfds_t nfd, int timeout)
   static HANDLE hEvent;
   WSANETWORKEVENTS ev;
   HANDLE h, handle_array[FD_SETSIZE + 2];
-  DWORD ret, wait_timeout, nhandles, start = 0, elapsed, orig_timeout = 0;
+  DWORD ret, wait_timeout, nhandles, orig_timeout = 0;
+  ULONGLONG start = 0;
   fd_set rfds, wfds, xfds;
   BOOL poll_again;
   MSG msg;
@@ -465,7 +469,7 @@ poll (struct pollfd *pfd, nfds_t nfd, int timeout)
   if (timeout != INFTIM)
     {
       orig_timeout = timeout;
-      start = GetTickCount();
+      start = GetTickCount64();
     }
 
   if (!hEvent)
@@ -614,8 +618,8 @@ restart:
 
   if (!rc && orig_timeout && timeout != INFTIM)
     {
-      elapsed = GetTickCount() - start;
-      timeout = elapsed >= orig_timeout ? 0 : orig_timeout - elapsed;
+      ULONGLONG elapsed = GetTickCount64() - start;
+      timeout = elapsed >= orig_timeout ? 0 : (int)(orig_timeout - elapsed);
     }
 
   if (!rc && timeout)