cygcheck's understanding of TZ

Edward McGuire cygwin.com@metaed.com
Thu Jun 9 19:27:00 GMT 2011


On Thu, Jun 9, 2011 at 13:08, Charles Wilson wrote:
> cygcheck.exe is not a cygwin program.  It is a native windows
> program, and thus either (a) uses Windows support for time zone
> data, not cygwin, or (b) has some special code to mimic cygwin's
> tz handling, which may not be up-to-par.  You'll have to check the
> source code to be sure, but I rather doubt (b).

cygcheck.cc:
[snip]
#include <sys/time.h>
[snip]
  time_t now;
[snip]
  printf ("\nCygwin Configuration Diagnostics\n");
  time (&now);
  printf ("Current System Time: %s\n", ctime (&now));

It's using C RTL calls. And cygcheck(1) is linked with msvcrt.dll,
not GNU, and therefore cygcheck(1) has Microsoft C RTL behavior.
Microsoft C RTL does not support the pathname syntax extension;
that's a GNU thing.

http://support.microsoft.com/kb/155293/a

Based on the article above, it seems the MS CRTL returns times that
are off by 1 hour if you set TZ and also have daylight saving time
enabled in the Date/Time control panel. That is almost certainly why
cygcheck(1) is returning GMT +1 hour instead of GMT when you pass it
an invalid TZ.

Cheers,

MetaEd

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