[tz] zdump bug?

Arthur David Olson arthurdavidolson at gmail.com
Sun Oct 28 23:25:17 UTC 2018

(A backward compatibility note: if tzloadbody is changed to treat non-slash
arguments as filenames that aren't relative to the default time zone
directory, it should probably be set up to also look in the default
directory to avoid breaking anything that counts on the current behavior.)


On Sun, Oct 28, 2018 at 7:21 PM Arthur David Olson <
arthurdavidolson at gmail.com> wrote:

> If this is a bug I'd characterize it as a localtime.c bug rather than a
> zdump bug.
> Note first that zdump arguments are time zone names rather than file
> names. However, the localtime.c code is prepared to use a zone name as the
> name of a file when appropriate. If a zdump argument beginning with a slash
> is passed to tzalloc, it will be taken as an absolute filename. But if a
> name does NOT begin with a slash (for example, "./New_York") it is taken as
> a name within the default time zone directory. In the case at hand, there's
> no "New_York" file in the default directory (although there is an
> "America/New_York" file), so the software punts to its default; thus the
> differing behaviors. The "taken as a name within the default time zone
> directory" behavior is arguably worng (and, even if not worng, might best
> be documented).
> The relevant code is in the "tzloadbody" function. There's some complexity
> in that code that may not be necessary. Since time zone code gets compiled
> into programs run with root privileges, we want to ensure that the real
> user is entitled to read a file specified as the source of time zone
> information; that's done with an "access" call. The code tries to avoid the
> access call in "safe" cases--cases where the file is sure to be somewhere
> under zoneinfo (not specified as an absolute file name, and with no
> possibility of a ".." in the name). If we're willing to call access in all
> cases, the code for avoiding the access call can go.
>     @dashdashado
> On Sun, Oct 28, 2018 at 6:31 PM Matt Johnson <mj1856 at hotmail.com> wrote:
>> I notice when I run zdump like this:
>> zdump /usr/share/zoneinfo/America/New_York
>> The output is normal:
>> America/New_York  Sun Oct 28 18:23:35 2018 EDT
>> But if I change to the America directory...
>> cd /usr/share/zoneinfo/America
>> zdump ./New_York
>> The output is missing the abbreviation:
>> ./New_York  Sun Oct 28 22:23:48 2018
>> Is this expected? Seems like a subtle bug to me.  The abbreviations are
>> also missing with -v output.
>> (Ran on Ubuntu Linux 16.04.5 LTS)
>> Thanks,
>> Matt
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