[tz] Question about bug seen in OpenBSD and FreeBSD related to tzname

[Paul Eggert]

On 11/20/19 12:17 AM, Andras Farkas wrote:
> Hello!  Earlier this month, I noticed bugs in OpenBSD and FreeBSD
> related to tzname's values.
> https://marc.info/?l=openbsd-bugs&m=157379849727998&w=2
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=241978
> I noticed that both those OSes share relevant code with tzcode.
> How would I best test this stuff out with a recent release of tzcode?
> (i.e. how to make sure I'm including headers only from the 2019c
> tarball and not from my OS, when possible)

The short answer is to run 'make date' in the tzdb distribution, to see 
how tzdb creates the 'date' program with its own code instead of the 
operating system's.

The longer answer is that tzcode doesn't provide its own <time.h> 
headers; it provides only alternative implementations, which you need to 
link to.  tzcode does provide a tzfile.h header, which you can include 
by using the -I option (but you probably don't want to be including it).