Fix tzdata update tools for 'backzone'.

To maintain the status quo, we need to pull in backzone file. This file
can't be built on its own, so the easiest fix is to give zic(1) all the
files at once.

We also now have a situation where we have links to links, so we need to
dereference them until we find actual data.

Bug: 18330681
Change-Id: I03f4aa8e6e23802dc35cbff2f74f325eb17d7b2b

2 files changed, 21 insertions, 11 deletions

diff --git a/libc/tools/zoneinfo/ZoneCompactor.java b/libc/tools/zoneinfo/ZoneCompactor.java
index bf3153e..2d598fe 100644
--- a/libc/tools/zoneinfo/ZoneCompactor.java
+++ b/libc/tools/zoneinfo/ZoneCompactor.java
@@ -132,9 +132,15 @@ public class ZoneCompactor {
         throw new RuntimeException("zone filename too long: " + zoneName.length());
       }
 
+      // Follow the chain of links to work out where the real data for this zone lives.
+      String actualZoneName = zoneName;
+      while (links.get(actualZoneName) != null) {
+        actualZoneName = links.get(actualZoneName);
+      }
+
       f.write(toAscii(new byte[MAXNAME], zoneName));
-      f.writeInt(offsets.get(zoneName));
-      f.writeInt(lengths.get(zoneName));
+      f.writeInt(offsets.get(actualZoneName));
+      f.writeInt(lengths.get(actualZoneName));
       f.writeInt(0); // Used to be raw GMT offset. No longer used.
     }
 
diff --git a/libc/tools/zoneinfo/update-tzdata.py b/libc/tools/zoneinfo/update-tzdata.py
index f5681be..330f166 100755
--- a/libc/tools/zoneinfo/update-tzdata.py
+++ b/libc/tools/zoneinfo/update-tzdata.py
@@ -13,8 +13,11 @@ import sys
 import tarfile
 import tempfile
 
-regions = ['africa', 'antarctica', 'asia', 'australasia', 'backward',
-           'etcetera', 'europe', 'northamerica', 'southamerica']
+regions = ['africa', 'antarctica', 'asia', 'australasia',
+           'etcetera', 'europe', 'northamerica', 'southamerica',
+           # These two deliberately come last so they override what came
+           # before (and each other).
+           'backward', 'backzone' ]
 
 def CheckDirExists(dir, dirname):
   if not os.path.isdir(dir):
@@ -49,16 +52,16 @@ def WriteSetupFile():
       fields = line.split()
       if fields:
         if fields[0] == 'Link':
-          links.append('%s %s %s\n' % (fields[0], fields[1], fields[2]))
+          links.append('%s %s %s' % (fields[0], fields[1], fields[2]))
           zones.append(fields[2])
         elif fields[0] == 'Zone':
           zones.append(fields[1])
   zones.sort()
 
   setup = open('setup', 'w')
-  for link in links:
-    setup.write(link)
-  for zone in zones:
+  for link in sorted(set(links)):
+    setup.write('%s\n' % link)
+  for zone in sorted(set(zones)):
     setup.write('%s\n' % zone)
   setup.close()
 
@@ -165,9 +168,10 @@ def BuildBionicToolsAndData(data_filename):
 
   print 'Calling zic(1)...'
   os.mkdir('data')
-  for region in regions:
-    if region != 'backward':
-      subprocess.check_call(['zic', '-d', 'data', 'extracted/%s' % region])
+  zic_inputs = [ 'extracted/%s' % x for x in regions ]
+  zic_cmd = ['zic', '-d', 'data' ]
+  zic_cmd.extend(zic_inputs)
+  subprocess.check_call(zic_cmd)
 
   WriteSetupFile()