Bug#790065: texinfo: please make the index output reproducible

[Chris Lamb <lamby@debian.org>]

Source: texinfo
Version: 5.9.96.dfsg.1-1
Severity: wishlist
Tags: patch
User: reproducible-builds@lists.alioth.debian.org
Usertags: toolchain
X-Debbugs-Cc: reproducible-builds@lists.alioth.debian.org

Hi,

While working on the "reproducible builds" effort [1], we have noticed
that texinfo generates indices in a non-deterministic order.

This appears to happen because the index sort is not stable with respect
to the line number, resulting in output non-determinstically changing
from:

  * Entry   (line 1)
  * Entry   (line 2)

and 

  * Entry   (line 2)
  * Entry   (line 1)

.. when the entry is the same string.

The attached patch adds the line number to the sort comparator. Once
applied, (some) packages using texinfo can be built reproducibly in
our reproducible toolchain.

 [1]: https://wiki.debian.org/ReproducibleBuilds


Regards,

-- 
      ,''`.
     : :'  :     Chris Lamb
     `. `'`      lamby@debian.org / chris-lamb.co.uk
       `-

diff --git a/tp/Texinfo/Structuring.pm b/tp/Texinfo/Structuring.pm
index 6ed1be2..c2ec017 100644
--- a/tp/Texinfo/Structuring.pm
+++ b/tp/Texinfo/Structuring.pm
@@ -1984,6 +1984,9 @@ sub _sort_index_entries($$)
   if ($res == 0) {
     $res = ($key1->{'number'} <=> $key2->{'number'});
   }
+  if ($res == 0) {
+    $res = ($key1->{'line_nr'} <=> $key2->{'line_nr'});
+  }
   return $res;
 }
 
@@ -2016,6 +2019,7 @@ sub _do_index_keys($$$)
   foreach my $index_name (keys(%$index_entries)) {
     foreach my $entry (@{$index_entries->{$index_name}}) {
       $entry->{'in_code'} = $index_names->{$entry->{'index_name'}}->{'in_code'};
+      $entry->{'line_nr'} = $entry->{'command'}->{'line_nr'}->{'line_nr'};
       $options->{'code'} = $entry->{'in_code'};
       $entry->{'key'} = Texinfo::Convert::Text::convert(
                               {'contents' => $entry->{'content'}}, $options);