Fix parsing of or groups in build-deps with ignored packages

If the last alternative(s) of an Or group is ignored, because it does
not match an architecture list, we would end up keeping the or flag,
effectively making the next AND an OR.

For example, when parsing (on amd64):

    debhelper (>= 9), libnacl-dev [amd64] | libnacl-dev [i386]
 => debhelper (>= 9), libnacl-dev |

Which can cause python-apt to crash.

Even worse:

     debhelper (>= 9), libnacl-dev [amd64] | libnacl-dev [i386], foobar
  => debhelper (>= 9), libnacl-dev [amd64] | foobar

By setting the previous alternatives Or flag to the current Or flag
if the current alternative is ignored, we solve the issue.

LP: #1694697

2 files changed, 69 insertions, 1 deletions

diff --git a/apt-pkg/deb/debsrcrecords.cc b/apt-pkg/deb/debsrcrecords.cc
index 5f0a75cd9..d664b609e 100644
--- a/apt-pkg/deb/debsrcrecords.cc
+++ b/apt-pkg/deb/debsrcrecords.cc
@@ -129,8 +129,18 @@ bool debSrcRecordParser::BuildDepends(std::vector<pkgSrcRecords::Parser::BuildDe
             return _error->Error("Problem parsing dependency: %s", fields[I]);
 	 rec.Type = I;
 
-	 if (rec.Package != "")
+	 // We parsed a package that was ignored (wrong architecture restriction
+	 // or something).
+	 if (rec.Package == "") {
+	    // If we are in an OR group, we need to set the "Or" flag of the
+	    // previous entry to our value.
+	    if (BuildDeps.size() > 0 && (BuildDeps[BuildDeps.size() - 1].Op & pkgCache::Dep::Or) == pkgCache::Dep::Or) {
+	       BuildDeps[BuildDeps.size() - 1].Op &= ~pkgCache::Dep::Or;
+	       BuildDeps[BuildDeps.size() - 1].Op |= (rec.Op & pkgCache::Dep::Or);
+	    }
+	 } else {
    	    BuildDeps.push_back(rec);
+	 }
 	 
    	 if (Start == Stop) 
 	    break;
diff --git a/test/integration/test-bug-lp1694697-build-dep-architecture-limited-alternative b/test/integration/test-bug-lp1694697-build-dep-architecture-limited-alternative
new file mode 100755
index 000000000..7f8e4ad3d
--- /dev/null
+++ b/test/integration/test-bug-lp1694697-build-dep-architecture-limited-alternative
@@ -0,0 +1,58 @@
+#!/bin/sh
+set -e
+
+TESTDIR="$(readlink -f "$(dirname "$0")")"
+. "$TESTDIR/framework"
+
+setupenvironment
+configarchitecture 'i386'
+
+
+insertpackage 'stable' 'build-depends' 'i386' '1'
+insertpackage 'stable' 'foo' 'i386' '1'
+insertinstalledpackage 'build-essential' 'i386' '1'
+
+setupaptarchive
+
+# This used to be interpreted as build-depends | foo
+cat > foobar.dsc <<EOF
+Format: 3.0 (native)
+Source: foobar
+Binary: foobar
+Architecture: all
+Version: 1
+Maintainer: Joe Sixpack <joe@example.org>
+Build-Depends: build-depends [i386] | build-depends [amd64], foo
+Standards-Version: 3.9.8
+EOF
+testsuccessequal "Note, using file './foobar.dsc' to get the build dependencies
+Reading package lists...
+Building dependency tree...
+The following NEW packages will be installed:
+  build-depends foo
+0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
+Inst build-depends (1 stable [i386])
+Inst foo (1 stable [i386])
+Conf build-depends (1 stable [i386])
+Conf foo (1 stable [i386])" aptget build-dep --simulate ./foobar.dsc
+
+
+# This caused a segmentation fault
+cat > foobar.dsc <<EOF
+Format: 3.0 (native)
+Source: foobar
+Binary: foobar
+Architecture: all
+Version: 1
+Maintainer: Joe Sixpack <joe@example.org>
+Build-Depends: build-depends [i386] | build-depends [amd64]
+Standards-Version: 3.9.8
+EOF
+testsuccessequal "Note, using file './foobar.dsc' to get the build dependencies
+Reading package lists...
+Building dependency tree...
+The following NEW packages will be installed:
+  build-depends
+0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
+Inst build-depends (1 stable [i386])
+Conf build-depends (1 stable [i386])" aptget build-dep --simulate ./foobar.dsc