Parse unsupported != relation in dependencies

libapt has a NotEquals relation for version constraints in
dependencies, which is used internally e.g. in the MultiArch
implementation, but this relation is not supported by Debian
policy and as such can not be used in packages.

Our parser here is extremely accepting, even unknown relations are
parsed as Equals relation – but the version that must match will be a
rather strange one…

For our own testcases and e.g. on the command line with 'satisfy' it
can make sense to have != available… and what strange things apt does
parsing unsupported relations is not really much of a concern. Real
packages will not have such relations anyhow as we are (mostly) just
a consumer, not a producer of packages and index files.

1 files changed, 11 insertions, 1 deletions

diff --git a/apt-pkg/deb/deblistparser.cc b/apt-pkg/deb/deblistparser.cc
index 8099b36e4..46c362952 100644
--- a/apt-pkg/deb/deblistparser.cc
+++ b/apt-pkg/deb/deblistparser.cc
@@ -522,7 +522,17 @@ const char *debListParser::ConvertRelation(const char *I,unsigned int &Op)
       Op = pkgCache::Dep::Equals;
       I++;
       break;
-      
+
+      // != is unsupported packaging
+      case '!':
+      if (*(I + 1) == '=')
+      {
+	 I = I + 2;
+	 Op = pkgCache::Dep::NotEquals;
+	 break;
+      }
+      [[fallthrough]];
+
       // HACK around bad package definitions
       default:
       Op = pkgCache::Dep::Equals;