From 455f2c6c92e42c1a9e31268cbd491ba661f99882 Mon Sep 17 00:00:00 2001 From: Michael G Schwern Date: Sun, 31 Jan 2010 02:53:43 -0800 Subject: [PATCH] gmtime/localtime are busted around 2**48 Michael G Schwern wrote: > Anyhow, I'm willing to let that drop, but I want figure out A) why its > failing so early because it might be masking a bug, this is not > predicted behavior, and most importantly B) to get it to error, or at > least warn. > > I know B is possible, I did it for Time::y2038. I'll figure that part > out and try to dig into A. I would like to call B a blocker for 5.12. Found the bug, patch attached. v_tm_tday is an NV, so casting time to an integer will cause an overflow 2**31 days after 1970 or somewhere between 2**47 and 2**48. Not sure why the compiler didn't warn about that. This makes it work until the year overflows. As for putting in a warning, there's two options: 1) A few days before the 32 bit year overflows. 2) At some reasonable point before there's too much floating point inaccuracy. The possibility of long doubles will make #2 difficult to nail down, but I'll be happy with +/- 2**53. -- 24. Must not tell any officer that I am smarter than they are, especially if it's true. -- The 213 Things Skippy Is No Longer Allowed To Do In The U.S. Army http://skippyslist.com/list/ From 9e940e610ac5b2fbb09a554f505963094a4a0745 Mon Sep 17 00:00:00 2001 From: Michael G. Schwern Date: Sun, 31 Jan 2010 02:24:50 -0800 Subject: [PATCH] Type conversion bug in gmtime64 that was causing it to crap out around 2**48 Signed-off-by: H.Merijn Brand --- time64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/time64.c b/time64.c index ca31acf..1d43f39 100644 --- a/time64.c +++ b/time64.c @@ -377,7 +377,7 @@ static struct TM *S_gmtime64_r (const Time64_T *in_time, struct TM *p) time = time >= 0 ? floor(time / 60.0) : ceil(time / 60.0); v_tm_hour = (int)fmod(time, 24.0); time = time >= 0 ? floor(time / 24.0) : ceil(time / 24.0); - v_tm_tday = (int)time; + v_tm_tday = time; WRAP (v_tm_sec, v_tm_min, 60); WRAP (v_tm_min, v_tm_hour, 60); -- 2.7.4