[PATCH] always reset DST rules during tzset

[Benjamin Peterson <benjamin@python.org>]

do_tzset() did't always reset the DST transition rules r0 and r1. That means the
rules from older TZ settings could leak into newer ones.

The following program demonstrates this bug. It should print out the same
timezone twice but doesn't due to the leaky state.

int main() {
	time_t t = 0;
	struct tm p;
	setenv("TZ", "STD-1DST", 1);
	localtime_r(&t, &p);
	printf("%s\n", p.tm_zone);
	setenv("TZ", "STD-1DST,M3.2.0,M11.1.0", 1);
	tzset();
	setenv("TZ", "STD-1DST", 1);
	localtime_r(&t, &p);
	printf("%s\n", p.tm_zone);
	return 0;
}
---
 src/time/__tz.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/time/__tz.c b/src/time/__tz.c
index 51e66514..3ccfdd5d 100644
--- a/src/time/__tz.c
+++ b/src/time/__tz.c
@@ -130,6 +130,9 @@ static void do_tzset()
 
 	if (old_tz && !strcmp(s, old_tz)) return;
 
+	memset(r0, 0, sizeof r0);
+	memset(r1, 0, sizeof r1);
+
 	if (zi) __munmap((void *)zi, map_size);
 
 	/* Cache the old value of TZ to check if it has changed. Avoid
@@ -194,7 +197,6 @@ static void do_tzset()
 			const unsigned char *p;
 			__tzname[0] = __tzname[1] = 0;
 			__daylight = __timezone = dst_off = 0;
-			for (i=0; i<5; i++) r0[i] = r1[i] = 0;
 			for (p=types; p<abbrevs; p+=6) {
 				if (!p[4] && !__tzname[0]) {
 					__tzname[0] = (char *)abbrevs + p[5];
-- 
2.17.1