bug#19874: 25.0.50; encode-time not working as expected

[Paul Eggert <eggert@cs.ucla.edu>]

Wolfgang Jenkner wrote:

> Thanks for the explanation!  However, there's no indication that mktime
> is buggy (all tests pass when adjusting time_t_min, time_t_max), while
> localtime (and localtime_r) certainly is.  Nevertheless, the configure
> test causes mktime to be replaced but not localtime_r, which is actually
> used in emacs.  If I may say so this seems a bit like pulling the wrong
> tooth ;-)

I suppose we could make Gnulib smarter, so that it replaces some other function 
if it finds a particular bug in mktime, a bug that can be chalked up to 
localtime_r etc.  However, the current approach is simpler to maintain and 
shouldn't hurt anything.  Ashish's problem seems not to be in mktime at all (nor 
in its replacement).

>> It also appears to be the case that FreeBSD 10.1's implementation of
>> putenv is buggy, and that this is what is breaking Emacs's time code
>> (as Emacs uses putenv to modify the TZ environment variable), but we
>> haven't gotten to the bottom of that yet.  I'll try to write a little
>> test program to narrow it down.
>
> But putenv is already replaced on my 10-STABLE system (and emacs trunk):
>
> $ nm src/emacs | grep putenv
> 00000000005b85a0 T rpl_putenv
> 0000000000527150 T xputenv

Yes, and that's because FreeBSD putenv is incompatible with GNU putenv; in GNU 
systems, putenv ("xxx") is equivalent to unsetenv ("xxx") but FreeBSD doesn't 
support this extension to POSIX.  I don't know whether Emacs needs this 
extension, but it shouldn't hurt to have it.

> Ah, and the OP's example actually seems to give the expected result here
> (my timezone is Europe/Vienna):

Yes.  I can't reproduce the problem either.  I finally got around to building a 
VM running FreeBSD 10.1 amd64, and I cannot reproduce the bug, even when 
/etc/localtime is a copy of /usr/share/zoneinfo/Asia/Kolkata and TZ is initially 
unset.  However, I am running it in a text window, not under Gtk3.

Perhaps Gtk3 is in some way interfering with Emacs's putenv substitute.