ar: Correct -N COUNT off-by-one

When using instance [COUNT], the instance check is wrong.
instance-- == 0 should be --instance == 0.

Add a testcase run-ar-N.sh that uses -N COUNT with extract and delete
operations checking the right instance was extracted and deleted.

https://sourceware.org/bugzilla/show_bug.cgi?id=28725

Reported-by: panxiaohe <panxh_ran@163.com>
Signed-off-by: Mark Wielaard <mark@klomp.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/tests/run-ar-N.sh b/tests/run-ar-N.sh
new file mode 100755
index 00000000..de8f62b3
--- /dev/null
+++ b/tests/run-ar-N.sh
@@ -0,0 +1,65 @@
+#! /usr/bin/env bash
+# Copyright (C) 2022 Mark J. Wielaard <mark@klomp.org>
+# This file is part of elfutils.
+#
+# This file is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# elfutils is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. $srcdir/test-subr.sh
+
+tempfiles testfile test.ar
+
+echo create test.ar with 3 testfile
+echo 1 > testfile
+testrun ${abs_top_builddir}/src/ar -vr test.ar testfile
+echo 2 > testfile
+testrun ${abs_top_builddir}/src/ar -vq test.ar testfile
+testrun ${abs_top_builddir}/src/ar -t test.ar
+echo 3 > testfile
+testrun ${abs_top_builddir}/src/ar -vq test.ar testfile
+testrun_compare ${abs_top_builddir}/src/ar -t test.ar << EOF
+testfile
+testfile
+testfile
+EOF
+
+echo list content of testfile 1 2 3
+testrun ${abs_top_builddir}/src/ar -vx -N 1 test.ar testfile
+diff -u testfile - << EOF
+1
+EOF
+testrun ${abs_top_builddir}/src/ar -vx -N 2 test.ar testfile
+diff -u testfile - << EOF
+2
+EOF
+testrun ${abs_top_builddir}/src/ar -vx -N 3 test.ar testfile
+diff -u testfile - << EOF
+3
+EOF
+
+echo delete testfile 2
+testrun ${abs_top_builddir}/src/ar -vd -N 2 test.ar testfile
+testrun_compare ${abs_top_builddir}/src/ar -t test.ar << EOF
+testfile
+testfile
+EOF
+testrun ${abs_top_builddir}/src/ar -vx -N 1 test.ar testfile
+diff -u testfile - << EOF
+1
+EOF
+testrun ${abs_top_builddir}/src/ar -vx -N 2 test.ar testfile
+diff -u testfile - << EOF
+3
+EOF
+
+exit 0