mktime, timegm: simplify merge to glibc

Move code around to make a merge to glibc easier to audit.
This should not change behavior.
* lib/mktime.c: Include more standard files unconditionally.
(NEED_MKTIME_INTERNAL, NEED_MKTIME_WINDOWS)
(NEED_MKTIME_WORKING): Give default values to pacify -Wundef,
which glibc uses.  Default NEED_MKTIME_WORKING to DEBUG_MKTIME, to
simplify later conditionals; default the others to zero.  In uses
of these conditionals, explicitly spell out how _LIBC affects
things, so it’s easier to review from a glibc viewpoint.
(my_tzset, __tzset) [!_LIBC]: New function and macro, to better
compartmentalize tzset issues.  Move system-dependent tzsettish
code here from mktime.
(mktime): Move tzsettish code to my_tzset, and move
localtime_offset to within mktime so that it doesn’t
need a separate ifdef.
* lib/mktime-internal.h (__gmtime_r, __localtime_r, __mktime_internal):
Move these macros here from lib/mktime.c and lib/gmtime.c.

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/mktime-internal.h b/lib/mktime-internal.h
index f531b55917..3e64156e8d 100644
--- a/lib/mktime-internal.h
+++ b/lib/mktime-internal.h
@@ -35,3 +35,19 @@ typedef int mktime_offset_t;
 time_t mktime_internal (struct tm *,
                         struct tm * (*) (time_t const *, struct tm *),
                         mktime_offset_t *);
+
+/* Although glibc source code uses leading underscores, Gnulib wants
+   ordinary names.
+
+   Portable standalone applications should supply a <time.h> that
+   declares a POSIX-compliant localtime_r, for the benefit of older
+   implementations that lack localtime_r or have a nonstandard one.
+   Similarly for gmtime_r.  See the gnulib time_r module for one way
+   to implement this.  */
+
+#undef __gmtime_r
+#undef __localtime_r
+#define __gmtime_r gmtime_r
+#define __localtime_r localtime_r
+
+#define __mktime_internal mktime_internal