From 6acdcc5a8ad4911db859088980f06f9f1f6e1532 Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Thu, 18 Dec 2025 13:41:38 +0100
Subject: [PATCH] patomic: Fix support for macOS pre-10.12

For now we will unconditionally use ulock APIs on arm64 (which requires macOS 11 anyway) and weak-link it (with fallback to pthreads implementation) on Intel

See also #1780
---
 dtool/src/dtoolbase/patomic.I   | 12 ++++++++++++
 dtool/src/dtoolbase/patomic.cxx |  2 +-
 dtool/src/dtoolbase/patomic.h   | 13 +++++++++----
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/dtool/src/dtoolbase/patomic.I b/dtool/src/dtoolbase/patomic.I
index d1395c9e90..b679834713 100644
--- a/dtool/src/dtoolbase/patomic.I
+++ b/dtool/src/dtoolbase/patomic.I
@@ -454,6 +454,12 @@ patomic_notify_one(volatile uint32_t *value) {
 #elif defined(_WIN32)
   _patomic_wake_one_func((void *)value);
 #elif defined(__APPLE__)
+#ifndef __arm64__
+  if (UNLIKELY(__ulock_wake == nullptr || __ulock_wait == nullptr)) {
+    _patomic_notify_all(value);
+    return;
+  }
+#endif
   __ulock_wake(UL_COMPARE_AND_WAIT, (void *)value, 0);
 #elif defined(HAVE_POSIX_THREADS)
   _patomic_notify_all(value);
@@ -472,6 +478,12 @@ patomic_notify_all(volatile uint32_t *value) {
 #elif defined(_WIN32)
   _patomic_wake_all_func((void *)value);
 #elif defined(__APPLE__)
+#ifndef __arm64__
+  if (UNLIKELY(__ulock_wake == nullptr || __ulock_wait == nullptr)) {
+    _patomic_notify_all(value);
+    return;
+  }
+#endif
   __ulock_wake(UL_COMPARE_AND_WAIT | ULF_WAKE_ALL, (void *)value, 0);
 #elif defined(HAVE_POSIX_THREADS)
   _patomic_notify_all(value);
diff --git a/dtool/src/dtoolbase/patomic.cxx b/dtool/src/dtoolbase/patomic.cxx
index 1b939a58c6..26949e564a 100644
--- a/dtool/src/dtoolbase/patomic.cxx
+++ b/dtool/src/dtoolbase/patomic.cxx
@@ -125,7 +125,7 @@ initialize_wait(volatile VOID *addr, PVOID cmp, SIZE_T size, DWORD timeout) {
   return emulated_wait(addr, cmp, size, timeout);
 }
 
-#elif !defined(CPPPARSER) && !defined(__linux__) && !defined(__APPLE__) && defined(HAVE_POSIX_THREADS)
+#elif !defined(CPPPARSER) && !defined(__linux__) && (!defined(__APPLE__) || !defined(__arm64__)) && defined(HAVE_POSIX_THREADS)
 
 // Same as above, but using pthreads.
 struct alignas(64) WaitTableEntry {
diff --git a/dtool/src/dtoolbase/patomic.h b/dtool/src/dtoolbase/patomic.h
index 02d1ab6ebc..2b0fdaacc0 100644
--- a/dtool/src/dtoolbase/patomic.h
+++ b/dtool/src/dtoolbase/patomic.h
@@ -36,9 +36,6 @@
 // Undocumented API, see https://outerproduct.net/futex-dictionary.html
 #define UL_COMPARE_AND_WAIT 1
 #define ULF_WAKE_ALL 0x00000100
-
-extern "C" int __ulock_wait(uint32_t op, void *addr, uint64_t value, uint32_t timeout);
-extern "C" int __ulock_wake(uint32_t op, void *addr, uint64_t wake_value);
 #endif
 
 #if defined(THREAD_DUMMY_IMPL) || defined(THREAD_SIMPLE_IMPL)
@@ -173,9 +170,17 @@ ALWAYS_INLINE void patomic_notify_all(volatile uint32_t *value);
 EXPCL_DTOOL_DTOOLBASE extern BOOL (__stdcall *_patomic_wait_func)(volatile VOID *, PVOID, SIZE_T, DWORD);
 EXPCL_DTOOL_DTOOLBASE extern void (__stdcall *_patomic_wake_one_func)(PVOID);
 EXPCL_DTOOL_DTOOLBASE extern void (__stdcall *_patomic_wake_all_func)(PVOID);
-#elif !defined(__linux__) && !defined(__APPLE__) && defined(HAVE_POSIX_THREADS)
+#elif defined(__APPLE__) && defined(__arm64__)
+extern "C" int __ulock_wait(uint32_t op, void *addr, uint64_t value, uint32_t timeout);
+extern "C" int __ulock_wake(uint32_t op, void *addr, uint64_t wake_value);
+#elif !defined(__linux__) && defined(HAVE_POSIX_THREADS)
 EXPCL_DTOOL_DTOOLBASE void _patomic_wait(const volatile uint32_t *value, uint32_t old);
 EXPCL_DTOOL_DTOOLBASE void _patomic_notify_all(volatile uint32_t *value);
+#ifdef __APPLE__
+// Use conditionally since we can't count on support before 10.12.
+extern "C" int __ulock_wait(uint32_t op, void *addr, uint64_t value, uint32_t timeout) __attribute__((weak_import));
+extern "C" int __ulock_wake(uint32_t op, void *addr, uint64_t wake_value) __attribute__((weak_import));
+#endif
 #endif
 
 #include "patomic.I"