Issue #7774: Set sys.executable to an empty string if argv[0] has been
set to an non existent program name and Python is unable to retrieve the real
program name.

Fix also sysconfig: if sys.executable is an empty string, use the current
working directory.
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 15b88ce..e41814b 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -437,6 +437,17 @@
         self.assertEqual(sys.call_tracing(str, (2,)), "2")
         self.assertRaises(TypeError, sys.call_tracing, str, 2)
 
+    def test_executable(self):
+        # Issue #7774: Ensure that sys.executable is an empty string if argv[0]
+        # has been set to an non existent program name and Python is unable to
+        # retrieve the real program name
+        import subprocess
+        p = subprocess.Popen(
+            ["nonexistent", "-c", 'import sys; print "executable=%r" % sys.executable'],
+            executable=sys.executable, stdout=subprocess.PIPE)
+        executable = p.communicate()[0].strip()
+        p.wait()
+        self.assertEqual(executable, "executable=''")
 
 class SizeofTest(unittest.TestCase):