Hi,

with Cygwin 1.5.25 I removed the link time reference to the non-standard
timezone() function in Cygwin.  Old applications are still able to use
it, but you don't get to it when building new applications.  Rather
timezone is now always a variable for newly build apps, as required by
POSIX.

However, the drawback is that suddenly ruby 1.8.6 doesn't build anymore.

Ruby on Cygwin uses the replacement function of strftime defined in
missing/strftime.c.  This function uses the timezone() function when
built on Cygwin.

While this seems to be fixed using finer grained configure checking in
the stable snapshots on the first glance, the created code is actually
doing nothing for the %Z format specifier.  From `gcc -E strftime.c':

  [...]
  case 'Z':
# 469 "./missing/strftime.c"
   break;

So the problem persists, just differently.

The question is this:  Why is Ruby on Cygwin using its own strftime at
all, instead of using Cygwin's strftime?

While looking into this, I found that Configure.in makes a few
assumptions about Cygwin which are incorrect:

  cygwin*)      rb_cv_have_daylight=no
                ac_cv_var_tzname=no
                ac_cv_func__setjmp=no
                ac_cv_func_setitimer=no
                ;;

and later:

  cygwin*)
    [...]
    AC_LIBOBJ([strftime])
    ;;

All of the above should actually go away.  Cygwin has the daylight
variable, tzname, _setjmp, setitimer, and, last but not least, strftime,
which has a POSIX compliant implementation of %Z.

Given that, I'd like to propose the below patch.  It's against the
stable release 1.8.6-p111, but AFAICS, it applies cleanly to
configure.in from the stable snapshot as well, just with offsets.

--- configure.in.ORIG   2008-01-08 13:11:13.583867700 +0100
+++ configure.in        2008-01-08 13:11:21.944438700 +0100
@@ -372,11 +372,7 @@ human*)            ac_cv_func_getpgrp_void=yes
                ac_cv_func_setitimer=no
                ;;
 beos*)         ac_cv_func_link=no;;
-cygwin*)       rb_cv_have_daylight=no
-               ac_cv_var_tzname=no
-               ac_cv_func__setjmp=no
-               ac_cv_func_setitimer=no
-               ;;
+cygwin*)       ;;
 mingw*)                if test "$with_winsock2" = yes; then
                  LIBS="-lws2_32 $LIBS"
                else
@@ -1461,7 +1457,6 @@ case "$target_os" in
                LIBRUBY_SO='cyg$(RUBY_SO_NAME)'${MAJOR}${MINOR}.dll
                LIBRUBY='lib$(RUBY_SO_NAME).dll.a'
            fi
-           AC_LIBOBJ([strftime])
            ;;
        mingw*)
            RUBY_SO_NAME=${rb_cv_msvcrt}-'$(RUBY_INSTALL_NAME)'${MAJOR}${MINOR}

If it's not ok to disable Ruby's own implementation of strftime on
Cygwin for some reason, then you should at least get rid of these two
lines in configure.in:

                rb_cv_have_daylight=no
                ac_cv_var_tzname=no

This results in a correct compilation of missing/strftime.c in the
stable snapshot.  The old missing/strftime.c in 1.8.6-p111 will still
not build, though.

Thanks,
Corinna