Bug#907264: faketime: timezone bugs: lax parsing, no way to specify UTC or TZ
Control: reassign 907264 libc6 2.33-7 Control: retitle 907264 glibc's strptime does not handle %z and %Z as expected Control: affects 907264 + faketime On Sat 2018-08-25 21:44:04 +0200, Wolfgang Hommel wrote: > Apparently, glibc goes for a new tm->tm_gmtoff field and supports %z > (but not %Z) fully yet. This might give some headaches regarding > cross-platform compatibility, and implementing a completely own parser > (i.e., not using strptime()) does not seem viable, either. So yes, this > needs to be addressed, but will take some time. Since the problem appears to be in strptime(), i'm reassigning this bug to glibc. --dkg signature.asc Description: PGP signature
Bug#907264: faketime: timezone bugs: lax parsing, no way to specify UTC or TZ
Ian, thanks for the detailed report, which is clearly to confirm. libfaketime internally relies on strptime() to parse the user-specified timestamp. On current macOS, your examples work reasonably well in the following variation: $ FAKETIME_FMT="%Y-%m-%d %T %z" ./faketime -f '2018-06-26 09:00:03 +0200' gdate -R Tue, 26 Jun 2018 09:00:03 +0200 $ FAKETIME_FMT="%Y-%m-%d %T %z" ./faketime -f '2018-06-26 09:00:03 +0300' gdate -R Tue, 26 Jun 2018 08:00:03 +0200 $ FAKETIME_FMT="%Y-%m-%d %T %z" ./faketime -f '2018-06-26 09:00:03 +0400' gdate -R Tue, 26 Jun 2018 07:00:03 +0200 Whereas on Debian, with the glibc implementation of strptime, we end up with your results: $ FAKETIME_FMT="%Y-%m-%d %T %z" ./faketime -f '2018-06-26 09:00:03 +0200' date -R Tue, 26 Jun 2018 09:00:03 +0200 $ FAKETIME_FMT="%Y-%m-%d %T %z" ./faketime -f '2018-06-26 09:00:03 +0300' date -R Tue, 26 Jun 2018 09:00:03 +0200 $ FAKETIME_FMT="%Y-%m-%d %T %z" ./faketime -f '2018-06-26 09:00:03 +0400' date -R Tue, 26 Jun 2018 09:00:03 +0200 Apparently, glibc goes for a new tm->tm_gmtoff field and supports %z (but not %Z) fully yet. This might give some headaches regarding cross-platform compatibility, and implementing a completely own parser (i.e., not using strptime()) does not seem viable, either. So yes, this needs to be addressed, but will take some time. As a workaround, you can throw anything at libfaketime what `date` can interpret, as in $ LD_PRELOAD=./libfaketime.so.1 FAKETIME_FMT=%s FAKETIME="`date +%s -d'2018-06-26 09:00:03+0400'`" date -R Tue, 26 Jun 2018 07:00:03 +0200 Best regards, Wolfgang
Bug#907264: faketime: timezone bugs: lax parsing, no way to specify UTC or TZ
Package: faketime Version: 0.9.6-7+b1 1. faketime does not properly validate the supplied advanced timestamp format: $ faketime -f '2018-06-26 09:00:03+02:00' date -R Tue, 26 Jun 2018 09:00:03 +0100 $ date -R -d '2018-06-26 09:00:03+02:00' Tue, 26 Jun 2018 08:00:03 +0100 $ 2. There is no way to specify a time which does not depend on the timezone in force. This is quite awkward, because there are some times which, in some timezones, cannot be represented in the offered `advanced timestamp format'. $ TZ=Europe/London date -d @$(( 1540683000 + 3600 * 0 )) -R Sun, 28 Oct 2018 00:30:00 +0100 $ TZ=Europe/London date -d @$(( 1540683000 + 3600 * 1 )) -R Sun, 28 Oct 2018 01:30:00 +0100 $ TZ=Europe/London date -d @$(( 1540683000 + 3600 * 2 )) -R Sun, 28 Oct 2018 01:30:00 + $ TZ=Europe/London date -d @$(( 1540683000 + 3600 * 3 )) -R Sun, 28 Oct 2018 02:30:00 + $ TZ=Europe/London faketime -f '2018-10-28 01:30:00' date -R Sun, 28 Oct 2018 01:30:00 + $ The problem is that "2018-10-28 01:30:00 London time" occurs twice, at both of Sun, 28 Oct 2018 01:30:00 +0100 = Sun, 28 Oct 2018 00:30:00 + and Sun, 28 Oct 2018 01:30:00 + faketime makes it impossible to specify the former. This can be worked around by saving and restoring TZ: env TZ=UTC faketime -f env TZ="$TZ" I suggest that these bugs be fixed by interpreting a numeric timezone offset in RFC3339 format, as shown above. This should be done for both the absolute frozen time, and the start-at timestamp. Thanks, Ian. -- System Information: Debian Release: 9.5 APT prefers stable-debug APT policy: (500, 'stable-debug'), (500, 'stable') Architecture: amd64 (x86_64) Foreign Architectures: i386 Kernel: Linux 4.16.0-0.bpo.2-amd64 (SMP w/4 CPU cores) Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE=C.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Init: sysvinit (via /sbin/init) Versions of packages faketime depends on: ii libc62.24-11+deb9u3 ii libfaketime 0.9.6-7+b1 faketime recommends no packages. faketime suggests no packages. -- no debconf information
