[Python-checkins] bpo-42814: Fix undefined behavior in Objects/genericaliasobject.c (GH-24073)

[vstinner]

https://github.com/python/cpython/commit/5d3553b0a8959e7505bbec4de03077dbf135ee4b
commit: 5d3553b0a8959e7505bbec4de03077dbf135ee4b
branch: master
author: Zackery Spytz <zspytz at gmail.com>
committer: vstinner <vstinner at python.org>
date: 2021-01-03T13:18:25+01:00
summary:

bpo-42814: Fix undefined behavior in Objects/genericaliasobject.c (GH-24073)

In is_typing_name(), va_end() is not always called before the
function returns.  It is undefined behavior to call va_start()
without also calling va_end().

files:
A Misc/NEWS.d/next/Core and Builtins/2021-01-03-04-41-25.bpo-42814.sDvVbb.rst
M Objects/genericaliasobject.c

diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-01-03-04-41-25.bpo-42814.sDvVbb.rst b/Misc/NEWS.d/next/Core and Builtins/2021-01-03-04-41-25.bpo-42814.sDvVbb.rst
new file mode 100644
index 0000000000000..6978c36f98c96
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-01-03-04-41-25.bpo-42814.sDvVbb.rst	
@@ -0,0 +1 @@
+Fix undefined behavior in ``Objects/genericaliasobject.c``.
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 4cc82ffcdf39a..8fae83b27297d 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -173,6 +173,7 @@ is_typing_name(PyObject *obj, int num, ...)
             break;
         }
     }
+    va_end(names);
     if (!hit) {
         return 0;
     }
@@ -184,7 +185,6 @@ is_typing_name(PyObject *obj, int num, ...)
         && _PyUnicode_EqualToASCIIString(module, "typing");
     Py_DECREF(module);
     
-    va_end(names);
     return res;
 }