sysv-generator: fix wrong "Overwriting existing symlink" warnings

Fix result testing of is_symlink() to ignore negative results, which happen if
the file name does not exist at all. In this case we do not want a warning and
unlink the non-existing link.

https://bugs.debian.org/778700

2 files changed, 8 insertions, 1 deletions

diff --git a/src/sysv-generator/sysv-generator.c b/src/sysv-generator/sysv-generator.c
index 2091854e08..bd67f321f6 100644
--- a/src/sysv-generator/sysv-generator.c
+++ b/src/sysv-generator/sysv-generator.c
@@ -166,7 +166,7 @@ static int generate_unit_file(SysvStub *s) {
         /* We might already have a symlink with the same name from a Provides:,
          * or from backup files like /etc/init.d/foo.bak. Real scripts always win,
          * so remove an existing link */
-        if (is_symlink(unit)) {
+        if (is_symlink(unit) > 0) {
                 log_warning("Overwriting existing symlink %s with real service", unit);
                 (void) unlink(unit);
         }
diff --git a/test/sysv-generator-test.py b/test/sysv-generator-test.py
index c6a8f1f21c..cf7d467368 100644
--- a/test/sysv-generator-test.py
+++ b/test/sysv-generator-test.py
@@ -178,6 +178,8 @@ class SysvGeneratorTest(unittest.TestCase):
         self.assertEqual(s.get('Service', 'ExecStop'),
                          '%s stop' % init_script)
 
+        self.assertNotIn('Overwriting', err)
+
     def test_simple_enabled_all(self):
         '''simple service without dependencies, enabled in all runlevels'''
 
@@ -185,6 +187,7 @@ class SysvGeneratorTest(unittest.TestCase):
         err, results = self.run_generator()
         self.assertEqual(list(results), ['foo.service'])
         self.assert_enabled('foo.service', ['multi-user', 'graphical'])
+        self.assertNotIn('Overwriting', err)
 
     def test_simple_enabled_some(self):
         '''simple service without dependencies, enabled in some runlevels'''
@@ -270,6 +273,7 @@ class SysvGeneratorTest(unittest.TestCase):
         for f in ['bar.service', 'baz.service']:
             self.assertEqual(os.readlink(os.path.join(self.out_dir, f)),
                              'foo.service')
+        self.assertNotIn('Overwriting', err)
 
     def test_same_provides_in_multiple_scripts(self):
         '''multiple init.d scripts provide the same name'''
@@ -289,6 +293,9 @@ class SysvGeneratorTest(unittest.TestCase):
         self.add_sysv('bar', {'Provides': 'bar'}, enable=True)
         err, results = self.run_generator()
         self.assertEqual(sorted(results), ['bar.service', 'foo.service'])
+        # we do expect an overwrite here, bar.service should overwrite the
+        # alias link from foo.service
+        self.assertIn('Overwriting', err)
 
     def test_nonexecutable_script(self):
         '''ignores non-executable init.d script'''