Issue #6271: mmap tried to close invalid file handle (-1) when annonymous.

(On Unix) Patch by STINNER Victor.

Misc/NEWS

@@ -325,6 +325,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #6271: mmap tried to close invalid file handle (-1) when annonymous.
+  (On Unix)
+
 - Issue #6215: All bug fixes and enhancements from the Python 3.1 io library
   (including the fast C implementation) have been backported to the standard
   ``io`` module.

Modules/mmapmodule.c

@@ -158,7 +158,8 @@ mmap_close_method(mmap_object *self, PyObject *unused)
 #endif /* MS_WINDOWS */
 
 #ifdef UNIX
-	(void) close(self->fd);
+	if (0 <= self->fd)
+		(void) close(self->fd);
 	self->fd = -1;
 	if (self->data != NULL) {
 		munmap(self->data, self->size);