[PATCH 1/1] poll: use GetTickCount64() to avoid wrap-around issues

From

Steve Hoelzer via GitGitGadget <gitgitgadget@gmail.com>

Date

Oct 31, 2018, 21:11 UTC

Message-ID

<69bc5924f94b56f92d9653b3a64f721bd03f1956.1541020294.git.gitgitgadget@gmail.com>

In-Reply-To

<pull.64.git.gitgitgadget@gmail.com>

From: Steve Hoelzer <shoelzer@gmail.com>

Reason: GetTickCount() overflows roughly every 49 days. Code that does
not take that into account can loop indefinitely. GetTickCount64()
operates on 64 bit values and does not have that problem.

Note: this patch has been carried in Git for Windows for almost two
years, but with a fallback for Windows XP, as the GetTickCount64()
function is only available on Windows Vista and later. However, in the
meantime we require Vista or later, hence we can drop that fallback.

Signed-off-by: Steve Hoelzer <shoelzer@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 compat/poll/poll.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/compat/poll/poll.c b/compat/poll/poll.c
index ad5dcde439..4abbfcb6a4 100644
--- 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, elapsed, 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)
@@ -614,7 +618,7 @@ restart:
 
   if (!rc && orig_timeout && timeout != INFTIM)
     {
-      elapsed = GetTickCount() - start;
+      elapsed = (DWORD)(GetTickCount64() - start);
       timeout = elapsed >= orig_timeout ? 0 : orig_timeout - elapsed;
     }
 

-- 
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