[commit: ghc] master: Fix #7087 (integer overflow in getDelayTarget()) (598ee1a)

[Simon Marlow]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/598ee1ad1b8de089a2ed207543761d617a90db52

>---------------------------------------------------------------

commit 598ee1ad1b8de089a2ed207543761d617a90db52
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Tue Jul 31 09:06:43 2012 +0100

    Fix #7087 (integer overflow in getDelayTarget())

>---------------------------------------------------------------

 includes/Rts.h     |    2 ++
 rts/posix/Select.c |   15 ++++++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/includes/Rts.h b/includes/Rts.h
index 501b9dc..c52fe63 100644
--- a/includes/Rts.h
+++ b/includes/Rts.h
@@ -156,6 +156,8 @@ void _assertFail(const char *filename, unsigned int linenum)
 #define TIME_RESOLUTION 1000000000
 typedef StgInt64 Time;
 
+#define TIME_MAX HS_INT64_MAX
+
 #if TIME_RESOLUTION == 1000000000
 // I'm being lazy, but it's awkward to define fully general versions of these
 #define TimeToUS(t)      ((t) / 1000)
diff --git a/rts/posix/Select.c b/rts/posix/Select.c
index 5acb817..99a9508 100644
--- a/rts/posix/Select.c
+++ b/rts/posix/Select.c
@@ -67,9 +67,18 @@ static LowResTime getLowResTimeOfDay(void)
  */
 LowResTime getDelayTarget (HsInt us)
 {
-    // round up the target time, because we never want to sleep *less*
-    // than the desired amount.
-    return TimeToLowResTimeRoundUp(getProcessElapsedTime() + USToTime(us));
+    Time elapsed;
+    elapsed = getProcessElapsedTime();
+
+    // If the desired target would be larger than the maximum Time,
+    // default to the maximum Time. (#7087)
+    if (us > TimeToUS(TIME_MAX - elapsed)) {
+        return TimeToLowResTimeRoundDown(TIME_MAX);
+    } else {
+        // round up the target time, because we never want to sleep *less*
+        // than the desired amount.
+        return TimeToLowResTimeRoundUp(elapsed + USToTime(us));
+    }
 }
 
 /* There's a clever trick here to avoid problems when the time wraps