From 171ba0504aa778d81346ea56fc9000b29d4d3e1d Mon Sep 17 00:00:00 2001
From: Victor Stinner <victor.stinner@haypocalc.com>
Date: Fri, 12 Mar 2010 14:20:59 +0000
Subject: [PATCH] Merged revisions 78835-78837 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/trunk

........
  r78835 | victor.stinner | 2010-03-11 13:34:39 +0100 (jeu., 11 mars 2010) | 7 lines

  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.
........
  r78836 | victor.stinner | 2010-03-11 14:27:35 +0100 (jeu., 11 mars 2010) | 4 lines

  Fix test_executable introduce in previous commit (r78835): Windows is able to
  retrieve the absolute Python path even if argv[0] has been set to a non
  existent program name.
........
  r78837 | victor.stinner | 2010-03-11 14:46:06 +0100 (jeu., 11 mars 2010) | 3 lines

  Another fix to test_executable() of test_sys: set the current working to avoid
  the #7774 bug.
........
---
 Lib/sysconfig.py     |  7 ++++++-
 Lib/test/test_sys.py | 17 +++++++++++++++++
 Modules/getpath.c    |  2 +-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/Lib/sysconfig.py b/Lib/sysconfig.py
index 619e4583bd0..0122f084765 100644
--- a/Lib/sysconfig.py
+++ b/Lib/sysconfig.py
@@ -84,7 +84,12 @@ _PREFIX = os.path.normpath(sys.prefix)
 _EXEC_PREFIX = os.path.normpath(sys.exec_prefix)
 _CONFIG_VARS = None
 _USER_BASE = None
-_PROJECT_BASE = os.path.dirname(realpath(sys.executable))
+if sys.executable:
+    _PROJECT_BASE = os.path.dirname(realpath(sys.executable))
+else:
+    # sys.executable can be empty if argv[0] has been changed and Python is
+    # unable to retrieve the real program name
+    _PROJECT_BASE = realpath(os.getcwd())
 
 if os.name == "nt" and "pcbuild" in _PROJECT_BASE[-8:].lower():
     _PROJECT_BASE = realpath(os.path.join(_PROJECT_BASE, pardir))
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index e20c95f0d31..eb0bef87313 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -479,6 +479,23 @@ class SysModuleTest(unittest.TestCase):
         out = p.communicate()[0].strip()
         self.assertEqual(out, b'?')
 
+    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
+        # For a normal installation, it should work without 'cwd'
+        # argument. For test runs in the build directory, see #7774.
+        python_dir = os.path.dirname(os.path.realpath(sys.executable))
+        p = subprocess.Popen(
+            ["nonexistent", "-c",
+             'import sys; print(sys.executable.encode("ascii", "backslashreplace"))'],
+            executable=sys.executable, stdout=subprocess.PIPE, cwd=python_dir)
+        stdout = p.communicate()[0]
+        executable = stdout.strip().decode("ASCII")
+        p.wait()
+        self.assertIn(executable, ["b''", repr(sys.executable.encode("ascii", "backslashreplace"))])
+
 
 class SizeofTest(unittest.TestCase):
 
diff --git a/Modules/getpath.c b/Modules/getpath.c
index a371cb37a5f..c6e50d3a573 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -522,7 +522,7 @@ calculate_path(void)
 	}
 	else
 		progpath[0] = '\0';
-	if (progpath[0] != SEP)
+	if (progpath[0] != SEP && progpath[0] != '\0')
 		absolutize(progpath);
 	wcsncpy(argv0_path, progpath, MAXPATHLEN);
 	argv0_path[MAXPATHLEN] = '\0';