[tz] [PROPOSED] zic option for including data from a certain year onward

[Christopher Wong]

Hi Paul,

I rebased to the latest, since your patch was already merged so I used it to test a bit. 

I am a bit confused about the result, maybe you can explain to me:

### Rule from africa:

# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
Zone	Africa/Abidjan	-0:16:08 -	LMT	1912
			 0:00	-	GMT

### Compiled data using @220924800 should correspond to 1977

for tz in etcetera southamerica northamerica europe africa antarctica  \
          asia australasia backward systemv factory; do
    ./zic -L /dev/null   -d $ZONEINFO  -r @220924800   -y "sh yearistype.sh" ${tz}
done
./zdump -v $ZONEINFO/Africa/Abidjan

### Got the following output:

/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  -9223372036854775808 = NULL
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  -9223372036854689408 = NULL
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  Fri Dec 31 23:59:59 1976 UT = Fri Dec 31 23:43:51 1976 LMT isdst=0 gmtoff=-968
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  Sat Jan  1 00:00:00 1977 UT = Sat Jan  1 00:00:00 1977 GMT isdst=0 gmtoff=0
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  9223372036854689407 = NULL
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  9223372036854775807 = NULL


### Compiled data using @441763200 should correspond to 1984

for tz in etcetera southamerica northamerica europe africa antarctica  \
          asia australasia backward systemv factory; do
    ./zic -L /dev/null   -d $ZONEINFO  -r @441763200   -y "sh yearistype.sh" ${tz}
done
./zdump -v $ZONEINFO/Africa/Abidjan

### Got the following output:

/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  -9223372036854775808 = NULL
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  -9223372036854689408 = NULL
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  Sat Dec 31 23:59:59 1983 UT = Sat Dec 31 23:43:51 1983 LMT isdst=0 gmtoff=-968
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  Sun Jan  1 00:00:00 1984 UT = Sun Jan  1 00:00:00 1984 GMT isdst=0 gmtoff=0
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  9223372036854689407 = NULL
/home/christwo/dists/tz/test_zic_github/Africa/Abidjan  9223372036854775807 = NULL

Is it correct that the switch between LMT to GMT is set to the specified start of the time range?

I also tried with the time range "-r @220924800/@441763200" then I encountered some segmentation fault error prints when I ran that. I haven't investigated any further on that.

BR,
Christopher Wong


________________________________________
From: Paul Eggert <eggert at cs.ucla.edu>
Sent: Saturday, March 9, 2019 06:34
To: Christopher Wong; Scott Nelson
Cc: Time Zone Mailing List
Subject: Re: [tz] [PROPOSED] zic option for including data from a certain year onward

Thanks for suggesting that. I looked into the issue, and it can be a trickier to
truncate the output because truncation also affects things like the default time
type and the TZ string, and truncation might affect the 32-bit data (which is
already truncated) differently from the 64-bit data. I wrote a different
implementation, which supports truncating newer timestamps as well, as per
Internet RFC 8536. Please give the attached proposed patch a try.