bug#23600: 25.1.50; encode-time returns wrong result

[Eli Zaretskii <eliz@gnu.org>]

> Cc: kzhr@d1.dion.ne.jp, 23600@debbugs.gnu.org
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sat, 4 Jun 2016 10:15:04 -0700
> 
> > Do callers of putenv expect the argument to be destroyed?
> 
> Yes and no. POSIX says that the environment can be modified in-place, so a 
> caller of putenv (S) should be prepared for *S to be modified (which is what I 
> assume you mean by "destroyed") because the string will be put into the 
> environment. Also, POSIX allows putenv to modify *S, as S is of type char * and 
> there is no prohibition in the standard against putenv modifying the pointed-to 
> storage. That being said, I don't know of any POSIXish implementation of putenv 
> (S) that modifies *S and I doubt whether any mainstream implementation would do 
> that.

Right, that's what I thought.

> Although the code you mention is stretching things a bit, it's not stretching 
> them beyond recognition: the intent of putenv ("TZ=<JST>-9") is not really "set 
> the 'TZ' value to the byte-string '<JST>-9' in the environment array", it's more 
> "set the time zone to 9 hours ahead of UTC and with abbreviation 'JST'", and on 
> MS-Windows the code implements this intent more faithfully than doing nothing would.

I think it would be cleaner if we copied the string before modifying
it.  I will do that when I have time.

Thanks.