Merge upstream main into gh-158907-proxy-auth-direct-407

Author: rajorin

Include/slots.h

@@ -42,7 +42,7 @@ struct PySlot {
 #define PySlot_STATIC_DATA(NAME, VALUE) \
     {.sl_id=(NAME), .sl_flags=PySlot_STATIC, .sl_ptr=(VALUE)}
 
-#define PySlot_END {0}
+#define PySlot_END {0, 0, {0}, {_Py_NULL}}
 
 
 // Macros without designated initializers (for C++11 and below):

Misc/NEWS.d/next/C_API/2026-10-05-17-09-35.gh-issue-149044.1HUiag.rst

@@ -0,0 +1,2 @@
+Fix the :c:macro:`PySlot_END` macro for C++: initialize all members to avoid
+compiler warnings. Patch by Victor Stinner.