Issue #19398: Extra slash no longer added to sys.path components in case of

empty compile-time PYTHONPATH components.  This fixes some tests in -S or -I
modes.

3 files changed, 11 insertions, 5 deletions

diff --git a/Lib/test/test_trace.py b/Lib/test/test_trace.py
index 1d894aaf84..1d87aea5a3 100644
--- a/Lib/test/test_trace.py
+++ b/Lib/test/test_trace.py
@@ -311,11 +311,11 @@ class TestCoverage(unittest.TestCase):
         with captured_stdout() as stdout:
             self._coverage(tracer)
         stdout = stdout.getvalue()
-        self.assertTrue("pprint.py" in stdout)
-        self.assertTrue("case.py" in stdout)   # from unittest
+        self.assertIn("pprint.py", stdout)
+        self.assertIn("case.py", stdout)   # from unittest
         files = os.listdir(TESTFN)
-        self.assertTrue("pprint.cover" in files)
-        self.assertTrue("unittest.case.cover" in files)
+        self.assertIn("pprint.cover", files)
+        self.assertIn("unittest.case.cover", files)
 
     def test_coverage_ignore(self):
         # Ignore all files, nothing should be traced nor printed
diff --git a/Misc/NEWS b/Misc/NEWS
index 15f5725955..cb244f3a35 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 3.6.0 beta 4
 Core and Builtins
 -----------------
 
+- Issue #19398: Extra slash no longer added to sys.path components in case of
+  empty compile-time PYTHONPATH components.
+
 - Issue #28583: PyDict_SetDefault didn't combine split table when needed.
   Patch by Xiang Zhang.
 
diff --git a/Modules/getpath.c b/Modules/getpath.c
index 65b47a3676..0f916436c5 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -762,7 +762,10 @@ calculate_path(void)
 
         if (defpath[0] != SEP) {
             wcscat(buf, prefix);
-            wcscat(buf, separator);
+            if (prefixsz >= 2 && prefix[prefixsz - 2] != SEP &&
+                defpath[0] != (delim ? DELIM : L'\0')) {  /* not empty */
+                wcscat(buf, separator);
+            }
         }
 
         if (delim) {