unstable mktime result

[Filipe Dias]

Hi all,

Mktime has different results when using dates that coincide with times that "didn't" exist due to a change of the reference for the specific timezone. In the examples I've run, when it's first called, it returns a past (IMHO invalid) value. After it's called for another date, calling it again for the first date, returns the expected result.

I found this happens on 1912-01-01 for Europe/Lisbon timezone and 1910-10-01 for Europe/Istanbul and it may be happening on other cases. I also found a similar case where it doesn't happen, 1940-05-15 for Europe/Amsterdam.

The tests I made are available here: https://gist.github.com/fmfdias/5c7c36726ff3cce12ead

Running them:
gcc test_europe_lisbon_glibc.c -o test_europe_lisbon_glibc
TZ='Europe/Lisbon' ./test_europe_lisbon_glibc

gcc test_europe_istanbul_glibc.c -o test_europe_istanbul_glibc
TZ='Europe/Istanbul' ./test_europe_istanbul_glibc

gcc test_europe_amsterdam_glibc.c -o test_europe_amsterdam_glibc
TZ='Europe/Amsterdam' ./test_europe_amsterdam_glibc

Although I run these tests on Ubuntu 14.10, I saw this also happening on a Ubuntu 12.04 machine.

lsb_release -rd
Description: Ubuntu 14.10
Release: 14.10

sudo apt-cache policy libc6
libc6:
  Installed: 2.19-10ubuntu2.3
  Candidate: 2.19-10ubuntu2.3
  Version table:
 *** 2.19-10ubuntu2.3 0
        500 http://archive.ubuntu.com/ubuntu/ utopic-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu/ utopic-security/main amd64 Packages
        100 /var/lib/dpkg/status
     2.19-10ubuntu2 0
        500 http://archive.ubuntu.com/ubuntu/ utopic/main amd64 Packages

Thank you!

[Andor Rozsnyai (arozsny)]

I had the I think the same problem with mktime().
(Ubuntu EGLIBC 2.19-0ubuntu6.8) 2.19

With input data:
struct tm testtime = {0};
    testtime.tm_year=10;
    testtime.tm_mon=0;
    testtime.tm_mday=1;
    testtime.tm_hour=0;
    testtime.tm_min=0;
    testtime.tm_sec=0;

mktime(t) int -1893459600 for "Europe/Budapest"
mktime(t) int -1893456000 for "Europe/London"
mktime(t) int -1893462264 ??? for "Europe/Bucharest"

for
struct tm testtime = {0};
    testtime.tm_year=50;
    testtime.tm_mon=0;
    testtime.tm_mday=1;
    testtime.tm_hour=0;
    testtime.tm_min=0;
    testtime.tm_sec=0;

mktime(t) int -631155600 for "Europe/Budapest"
mktime(t) int -631152000 for "Europe/London"
mktime(t) int -631159200 for "Europe/Bucharest"
mktime(t) int -631134000 for "America/Nipigon"