[tz] [PROPOSED] Fix 'zic -b slim' bug with TZ='CET'

[Paul Eggert]

Without this fix, 'zic -b slim' can mishandle transitions in the
few obsolescent zones like CET that do not start with local mean time.
For example, for CET it incorrectly optimizes away the first and
third transitions, and treats the second transition as one to
standard time instead of to DST.
* zic.c (swaptypes): Remove.  All uses removed.
(writezone): Swap indices rather than contents of the old type 0
and the new (default) type 0 array entries.
---
 zic.c | 44 +++++++++++++++++++-------------------------
 1 file changed, 19 insertions(+), 25 deletions(-)

diff --git a/zic.c b/zic.c
index 34228a5..03f33ee 100644
--- a/zic.c
+++ b/zic.c
@@ -1810,17 +1810,6 @@ atcomp(const void *avp, const void *bvp)
 	return (a < b) ? -1 : (a > b);
 }
 
-static void
-swaptypes(int i, int j)
-{
-  { zic_t t = gmtoffs[i]; gmtoffs[i] = gmtoffs[j]; gmtoffs[j] = t; }
-  { char t = isdsts[i]; isdsts[i] = isdsts[j]; isdsts[j] = t; }
-  { unsigned char t = abbrinds[i]; abbrinds[i] = abbrinds[j];
-    abbrinds[j] = t; }
-  { bool t = ttisstds[i]; ttisstds[i] = ttisstds[j]; ttisstds[j] = t; }
-  { bool t = ttisgmts[i]; ttisgmts[i] = ttisgmts[j]; ttisgmts[j] = t; }
-}
-
 struct timerange {
   int defaulttype;
   ptrdiff_t base, count;
@@ -2066,7 +2055,6 @@ writezone(const char *const name, const char *const string, char version,
 		   THISDEFAULTTYPE appears as type 0 in the output instead
 		   of OLD0.  TYPEMAP also omits unused types.  */
 		old0 = strlen(omittype);
-		swaptypes(old0, thisdefaulttype);
 
 #ifndef LEAVE_SOME_PRE_2011_SYSTEMS_IN_THE_LURCH
 		/*
@@ -2085,12 +2073,16 @@ writezone(const char *const name, const char *const string, char version,
 				if (isdsts[types[i]])
 					mrudst = types[i];
 				else	mrustd = types[i];
-			for (i = old0; i < typecnt; i++)
-				if (!omittype[i]) {
-					if (isdsts[i])
-						hidst = i;
-					else	histd = i;
-				}
+			for (i = old0; i < typecnt; i++) {
+			  int h = (i == old0 ? thisdefaulttype
+				   : i == thisdefaulttype ? old0 : i);
+			  if (!omittype[h]) {
+			    if (isdsts[h])
+			      hidst = i;
+			    else
+			      histd = i;
+			  }
+			}
 			if (hidst >= 0 && mrudst >= 0 && hidst != mrudst &&
 				gmtoffs[hidst] != gmtoffs[mrudst]) {
 					isdsts[mrudst] = -1;
@@ -2204,12 +2196,15 @@ writezone(const char *const name, const char *const string, char version,
 		if (hicut)
 		  putc(currenttype, fp);
 
-		for (i = old0; i < typecnt; i++)
-			if (!omittype[i]) {
-				puttzcode(gmtoffs[i], fp);
-				putc(isdsts[i], fp);
-				putc((unsigned char) indmap[abbrinds[i]], fp);
-			}
+		for (i = old0; i < typecnt; i++) {
+		  int h = (i == old0 ? thisdefaulttype
+			   : i == thisdefaulttype ? old0 : i);
+		  if (!omittype[h]) {
+		    puttzcode(gmtoffs[h], fp);
+		    putc(isdsts[h], fp);
+		    putc(indmap[abbrinds[h]], fp);
+		  }
+		}
 		if (thischarcnt != 0)
 			fwrite(thischars, sizeof thischars[0],
 				      thischarcnt, fp);
@@ -2244,7 +2239,6 @@ writezone(const char *const name, const char *const string, char version,
 		  for (i = old0; i < typecnt; i++)
 			if (!omittype[i])
 				putc(ttisgmts[i], fp);
-		swaptypes(old0, thisdefaulttype);
 	}
 	fprintf(fp, "\n%s\n", string);
 	close_file(fp, directory, name);
-- 
2.21.0