issue #3554: ctypes.string_at and ctypes.wstring_at must use the

pythonapi calling convention so that the GIL is held and error return
values are checked.

2 files changed, 6 insertions, 2 deletions

diff --git a/Lib/ctypes/__init__.py b/Lib/ctypes/__init__.py
index ef90bc7b87..7ad9e2be19 100644
--- a/Lib/ctypes/__init__.py
+++ b/Lib/ctypes/__init__.py
@@ -485,7 +485,7 @@ _cast = PYFUNCTYPE(py_object, c_void_p, py_object, py_object)(_cast_addr)
 def cast(obj, typ):
     return _cast(obj, obj, typ)
 
-_string_at = CFUNCTYPE(py_object, c_void_p, c_int)(_string_at_addr)
+_string_at = PYFUNCTYPE(py_object, c_void_p, c_int)(_string_at_addr)
 def string_at(ptr, size=-1):
     """string_at(addr[, size]) -> string
 
@@ -497,7 +497,7 @@ try:
 except ImportError:
     pass
 else:
-    _wstring_at = CFUNCTYPE(py_object, c_void_p, c_int)(_wstring_at_addr)
+    _wstring_at = PYFUNCTYPE(py_object, c_void_p, c_int)(_wstring_at_addr)
     def wstring_at(ptr, size=-1):
         """wstring_at(addr[, size]) -> string
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 954ae7e4ad..82c579d0b8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -77,6 +77,10 @@ Core and builtins
 Library
 -------
 
+- Issue #3554: ctypes.string_at and ctypes.wstring_at did call Python
+  api functions without holding the GIL, which could lead to a fatal
+  error when they failed.
+
 - Issue #2234: distutils failed for some versions of the cygwin compiler. The
   version reported by these tools does not necessarily follow the python
   version numbering scheme, so the module is less strict when parsing it.