[tz] [PROPOSED] Simplify zdump average-taking

[Paul Eggert]

* zdump.c (hunt): Simplify slightly, so that one more instruction
can be int width rather than time_t width if that’s what the
compiler prefers.  No need to mention C89 in the comment, as C89
support is going away soon.  (The code still happens to work in
C89, for what it’s worth.)
---
 zdump.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/zdump.c b/zdump.c
index a020102..04953dc 100644
--- a/zdump.c
+++ b/zdump.c
@@ -732,13 +732,9 @@ hunt(timezone_t tz, time_t lot, time_t hit, bool only_ok)
 
 	for ( ; ; ) {
 		/* T = average of LOT and HIT, rounding down.
-		   Avoid overflow, even on oddball C89 platforms
-		   where / rounds down and TIME_T_MIN == -TIME_T_MAX
-		   so lot / 2 + hit / 2 might overflow.  */
-		time_t t = (lot / 2
-			    - ((lot % 2 + hit % 2) < 0)
-			    + ((lot % 2 + hit % 2) == 2)
-			    + hit / 2);
+		   Avoid overflow.  */
+		int rem_sum = lot % 2 + hit % 2;
+		time_t t = (rem_sum == 2) - (rem_sum < 0) + lot / 2 + hit / 2;
 		if (t == lot)
 			break;
 		tm_ok = my_localtime_rz(tz, &t, &tm) != NULL;
-- 
2.38.1