[libc++] Make std::align an inline function from v2 ABI

Author: poor-circle

libcxx/include/__memory/align.h

@@ -11,14 +11,33 @@
 
 #include <__config>
 #include <__cstddef/size_t.h>
+#include <cstdint>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _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
 

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