fix nightly ci (#4816)

Author: Icxolu

pyo3-build-config/src/lib.rs

@@ -156,6 +156,10 @@ pub fn print_feature_cfgs() {
     if rustc_minor_version >= 79 {
         println!("cargo:rustc-cfg=diagnostic_namespace");
     }
+
+    if rustc_minor_version >= 85 {
+        println!("cargo:rustc-cfg=fn_ptr_eq");
+    }
 }
 
 /// Registers `pyo3`s config names as reachable cfg expressions
@@ -180,6 +184,7 @@ pub fn print_expected_cfgs() {
     println!("cargo:rustc-check-cfg=cfg(diagnostic_namespace)");
     println!("cargo:rustc-check-cfg=cfg(c_str_lit)");
     println!("cargo:rustc-check-cfg=cfg(rustc_has_once_lock)");
+    println!("cargo:rustc-check-cfg=cfg(fn_ptr_eq)");
 
     // allow `Py_3_*` cfgs from the minimum supported version up to the
     // maximum minor version (+1 for development for the next)

src/impl_/pymethods.rs

@@ -21,6 +21,7 @@ use std::panic::{catch_unwind, AssertUnwindSafe};
 use std::ptr::null_mut;
 
 use super::trampoline;
+use crate::internal_tricks::{clear_eq, traverse_eq};
 
 /// Python 3.8 and up - __ipow__ has modulo argument correctly populated.
 #[cfg(Py_3_8)]
@@ -364,7 +365,7 @@ unsafe fn call_super_traverse(
     // First find the current type by the current_traverse function
     loop {
         traverse = get_slot(ty, TP_TRAVERSE);
-        if traverse == Some(current_traverse) {
+        if traverse_eq(traverse, current_traverse) {
             break;
         }
         ty = get_slot(ty, TP_BASE);
@@ -375,7 +376,7 @@ unsafe fn call_super_traverse(
     }
 
     // Get first base which has a different traverse function
-    while traverse == Some(current_traverse) {
+    while traverse_eq(traverse, current_traverse) {
         ty = get_slot(ty, TP_BASE);
         if ty.is_null() {
             break;
@@ -429,7 +430,7 @@ unsafe fn call_super_clear(
     // First find the current type by the current_clear function
     loop {
         clear = ty.get_slot(TP_CLEAR);
-        if clear == Some(current_clear) {
+        if clear_eq(clear, current_clear) {
             break;
         }
         let base = ty.get_slot(TP_BASE);
@@ -441,7 +442,7 @@ unsafe fn call_super_clear(
     }
 
     // Get first base which has a different clear function
-    while clear == Some(current_clear) {
+    while clear_eq(clear, current_clear) {
         let base = ty.get_slot(TP_BASE);
         if base.is_null() {
             break;

src/internal_tricks.rs

@@ -1,4 +1,4 @@
-use crate::ffi::{Py_ssize_t, PY_SSIZE_T_MAX};
+use crate::ffi::{self, Py_ssize_t, PY_SSIZE_T_MAX};
 pub struct PrivateMarker;
 
 macro_rules! private_decl {
@@ -47,3 +47,31 @@ pub(crate) const fn ptr_from_ref<T>(t: &T) -> *const T {
 pub(crate) fn ptr_from_mut<T>(t: &mut T) -> *mut T {
     t as *mut T
 }
+
+// TODO: use ptr::fn_addr_eq on MSRV 1.85
+pub(crate) fn clear_eq(f: Option<ffi::inquiry>, g: ffi::inquiry) -> bool {
+    #[cfg(fn_ptr_eq)]
+    {
+        let Some(f) = f else { return false };
+        std::ptr::fn_addr_eq(f, g)
+    }
+
+    #[cfg(not(fn_ptr_eq))]
+    {
+        f == Some(g)
+    }
+}
+
+// TODO: use ptr::fn_addr_eq on MSRV 1.85
+pub(crate) fn traverse_eq(f: Option<ffi::traverseproc>, g: ffi::traverseproc) -> bool {
+    #[cfg(fn_ptr_eq)]
+    {
+        let Some(f) = f else { return false };
+        std::ptr::fn_addr_eq(f, g)
+    }
+
+    #[cfg(not(fn_ptr_eq))]
+    {
+        f == Some(g)
+    }
+}