[libcxx-commits] [libcxx] [libc++] Make std::align an inline function from v2 ABI (PR #167472)

[via libcxx-commits]

https://github.com/poor-circle updated https://github.com/llvm/llvm-project/pull/167472

>From 615eee277a552d4211607745f8599909c7c3ddd3 Mon Sep 17 00:00:00 2001
From: "zezheng.li" <lizezheng.lzz at alibaba-inc.com>
Date: Tue, 11 Nov 2025 18:07:31 +0800
Subject: [PATCH] [libc++] Make std::align an inline function from v2 ABI

---
 libcxx/include/__memory/align.h | 19 +++++++++++++++++++
 libcxx/src/memory.cpp           |  3 +++
 2 files changed, 22 insertions(+)

diff --git a/libcxx/include/__memory/align.h b/libcxx/include/__memory/align.h
index 402eac3380925..6c8e21be03f76 100644
--- a/libcxx/include/__memory/align.h
+++ b/libcxx/include/__memory/align.h
@@ -11,6 +11,7 @@
 
 #include <__config>
 #include <__cstddef/size_t.h>
+#include <cstdint>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -18,7 +19,25 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+// From >=v2 ABI, std::align is an inline function.
+#if _LIBCPP_ABI_VERSION >= 2
+inline _LIBCPP_HIDE_FROM_ABI void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space) {
+  void* __r = nullptr;
+  if (__sz <= __space) {
+    char* __p1 = static_cast<char*>(__ptr);
+    char* __p2 = reinterpret_cast<char*>(reinterpret_cast<uintptr_t>(__p1 + (__align - 1)) & -__align);
+    size_t __d = static_cast<size_t>(__p2 - __p1);
+    if (__d <= __space - __sz) {
+      __r   = __p2;
+      __ptr = __r;
+      __space -= __d;
+    }
+  }
+  return __r;
+}
+#else
 _LIBCPP_EXPORTED_FROM_ABI void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space);
+#endif
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/libcxx/src/memory.cpp b/libcxx/src/memory.cpp
index 9be40cb9c1285..9efbb6eb8eca3 100644
--- a/libcxx/src/memory.cpp
+++ b/libcxx/src/memory.cpp
@@ -132,6 +132,8 @@ __sp_mut& __get_sp_mut(const void* p) {
 
 #endif // _LIBCPP_HAS_THREADS
 
+// Remove std::align from >=v2 dylib ABI, make it an inline function.
+#if _LIBCPP_ABI_VERSION == 1
 void* align(size_t alignment, size_t size, void*& ptr, size_t& space) {
   void* r = nullptr;
   if (size <= space) {
@@ -146,5 +148,6 @@ void* align(size_t alignment, size_t size, void*& ptr, size_t& space) {
   }
   return r;
 }
+#endif
 
 _LIBCPP_END_NAMESPACE_STD