diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 8ba7fa2479d04..3a24b234263ab 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -927,6 +927,8 @@ ASTContext::getFeatureAvailInfo(Decl *D) const {
   auto *Attr = VD->getAttr<AvailabilityDomainAttr>();
   if (!Attr)
     return {};
+  if (!VD->getInit())
+    return {};
   StringRef Name = Attr->getName()->getName();
   auto *Init = cast<InitListExpr>(VD->getInit());
   Expr::EvalResult Result;
diff --git a/clang/lib/Headers/CMakeLists.txt b/clang/lib/Headers/CMakeLists.txt
index 6a19f20695b5d..905d432c8fbe9 100644
--- a/clang/lib/Headers/CMakeLists.txt
+++ b/clang/lib/Headers/CMakeLists.txt
@@ -37,6 +37,7 @@ set(core_files
   unwind.h
   varargs.h
   feature-availability.h
+  availability_domain.h
   )
 
 set(arm_common_files
diff --git a/clang/lib/Headers/availability_domain.h b/clang/lib/Headers/availability_domain.h
new file mode 100644
index 0000000000000..ede75841e2b97
--- /dev/null
+++ b/clang/lib/Headers/availability_domain.h
@@ -0,0 +1,53 @@
+/*===---- availability_domain.h - Availability Domain -----------------------===
+ *
+ * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+ * See https://llvm.org/LICENSE.txt for license information.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ *
+ *===-----------------------------------------------------------------------===
+ */
+
+#ifndef __AVAILABILITY_DOMAIN_H
+#define __AVAILABILITY_DOMAIN_H
+
+#include <stdint.h>
+
+#define __AVAILABILITY_DOMAIN_ENABLED 0
+#define __AVAILABILITY_DOMAIN_DISABLED 1
+#define __AVAILABILITY_DOMAIN_DYNAMIC 2
+
+/// Describes the fields of a Clang availability domain. This struct is an
+/// implementation detail of the compiler and is subject to change so don't
+/// reference `__AvailabilityDomain` directly. Instead, use the provided macros:
+///
+///     CLANG_DYNAMIC_AVAILABILITY_DOMAIN(MyDomain, query);
+///
+struct __AvailabilityDomain {
+  /// The state of the domain (AVAILABLE, UNAVAILABLE, DYNAMIC, etc.).
+  intptr_t state;
+  /// An optional function pointer to call to query the availability of a domain
+  /// at runtime. This should only be non-null for domains in the DYNAMIC state.
+  int (*const runtimeQuery)(void);
+};
+
+#define CLANG_DYNAMIC_AVAILABILITY_DOMAIN(domain, query)                       \
+  static struct __AvailabilityDomain domain __attribute__((                    \
+      availability_domain(domain))) = {__AVAILABILITY_DOMAIN_DYNAMIC, query}
+
+#define CLANG_ENABLED_AVAILABILITY_DOMAIN(domain)                              \
+  static struct __AvailabilityDomain domain __attribute__((                    \
+      availability_domain(domain))) = {__AVAILABILITY_DOMAIN_ENABLED, 0}
+
+#define CLANG_DISABLED_AVAILABILITY_DOMAIN(domain)                             \
+  static struct __AvailabilityDomain domain __attribute__((                    \
+      availability_domain(domain))) = {__AVAILABILITY_DOMAIN_DISABLED, 0}
+
+#define CLANG_ALWAYS_ENABLED_AVAILABILITY_DOMAIN(domain)                       \
+  static struct __AvailabilityDomain domain __attribute__((                    \
+      availability_domain(domain))) = {__AVAILABILITY_DOMAIN_ENABLED, 0}
+
+#define CLANG_ALWAYS_DISABLED_AVAILABILITY_DOMAIN(domain)                      \
+  static struct __AvailabilityDomain domain __attribute__((                    \
+      availability_domain(domain))) = {__AVAILABILITY_DOMAIN_DISABLED, 0}
+
+#endif /* __AVAILABILITY_DOMAIN_H */
diff --git a/clang/lib/Headers/feature-availability.h b/clang/lib/Headers/feature-availability.h
index 31abd2e4e081b..6532352f5e855 100644
--- a/clang/lib/Headers/feature-availability.h
+++ b/clang/lib/Headers/feature-availability.h
@@ -10,24 +10,8 @@
 #ifndef __FEATURE_AVAILABILITY_H
 #define __FEATURE_AVAILABILITY_H
 
-#include <stdint.h>
+// feature-availability.h is deprecated - use availability_domain.h instead.
 
-/// The possible availability domain states. These values are hardcoded in the
-/// compiler and reproduced here for convenience when defining domains.
-
-#define __AVAILABILITY_DOMAIN_ENABLED 0
-#define __AVAILABILITY_DOMAIN_DISABLED 1
-#define __AVAILABILITY_DOMAIN_DYNAMIC 2
-
-/// A struct describing availability domain definitions. This struct definition
-/// is just a convenience to ensure that a header defining an availability
-/// domain can define it with the arguments that Clang expects at parse time.
-struct __AvailabilityDomain {
-  /// The state of the domain (AVAILABLE, UNAVAILABLE, DYNAMIC, etc.).
-  intptr_t state;
-  /// An optional function pointer to call to query the availability of a domain
-  /// at runtime. This should only be non-null for domains in the DYNAMIC state.
-  int (*const runtimeQuery)(void);
-};
+#include <availability_domain.h>
 
 #endif /* __FEATURE_AVAILABILITY_H */
diff --git a/clang/lib/Headers/module.modulemap b/clang/lib/Headers/module.modulemap
index b196baf1b648f..7fbe87c530472 100644
--- a/clang/lib/Headers/module.modulemap
+++ b/clang/lib/Headers/module.modulemap
@@ -342,6 +342,11 @@ module feature_availability {
   export *
 }
 
+module availability_domain {
+  header "availability_domain.h"
+  export *
+}
+
 /* TO_UPSTREAM(BoundsSafety) ON */
 module ptrcheck {
   header "ptrcheck.h"
diff --git a/clang/test/CodeGen/feature-availability.c b/clang/test/CodeGen/feature-availability.c
index adcd6d9d56a1b..4f7d448a6986d 100644
--- a/clang/test/CodeGen/feature-availability.c
+++ b/clang/test/CodeGen/feature-availability.c
@@ -15,15 +15,15 @@
 #ifndef HEADER
 #define HEADER
 
-#include <feature-availability.h>
+#include <availability_domain.h>
 
 #define AVAIL 0
 
 #ifdef USE_DOMAIN
 // DOMAIN: @g3 = extern_weak global i32, align 4
 
-static struct __AvailabilityDomain feature1 __attribute__((availability_domain(feature1))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
-static struct __AvailabilityDomain feature2 __attribute__((availability_domain(feature2))) = {__AVAILABILITY_DOMAIN_DISABLED, 0};
+CLANG_ENABLED_AVAILABILITY_DOMAIN(feature1);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(feature2);
 #endif
 
 __attribute__((availability(domain:feature1, AVAIL))) int func0(void);
@@ -94,7 +94,7 @@ void test3(struct S0 *s0) {
 // DOMAIN-NEXT: ret void
 
 int pred1(void);
-static struct __AvailabilityDomain feature3 __attribute__((availability_domain(feature3))) = {__AVAILABILITY_DOMAIN_DYNAMIC, pred1};
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(feature3, pred1);
 __attribute__((availability(domain:feature3, AVAIL))) int func3(void);
 __attribute__((availability(domain:feature3, AVAIL))) extern int g3;
 
diff --git a/clang/test/CodeGenObjC/feature-availability.m b/clang/test/CodeGenObjC/feature-availability.m
index 14d5c83e42b52..5dd61fe7297bd 100644
--- a/clang/test/CodeGenObjC/feature-availability.m
+++ b/clang/test/CodeGenObjC/feature-availability.m
@@ -1,16 +1,14 @@
 // RUN: %clang_cc1 -triple arm64-apple-macosx -fblocks -ffeature-availability=feature1:on -ffeature-availability=feature2:off -ffeature-availability=feature3:on -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple arm64-apple-macosx -fblocks -emit-llvm -o - -DUSE_DOMAIN %s | FileCheck %s
 
-#include <feature-availability.h>
+#include <availability_domain.h>
 
 #define AVAIL 0
 
 #ifdef USE_DOMAIN
-int pred1(void);
-
-static struct __AvailabilityDomain feature1 __attribute__((availability_domain(feature1))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
-static struct __AvailabilityDomain feature2 __attribute__((availability_domain(feature2))) = {__AVAILABILITY_DOMAIN_DISABLED, 0};
-static struct __AvailabilityDomain feature3 __attribute__((availability_domain(feature3))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
+CLANG_ENABLED_AVAILABILITY_DOMAIN(feature1);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(feature2);
+CLANG_ENABLED_AVAILABILITY_DOMAIN(feature3);
 #endif
 
 // CHECK: @"OBJC_IVAR_$_C0._prop0" = hidden global i32 4, section "__DATA, __objc_ivar", align 4
diff --git a/clang/test/Modules/Inputs/feature-availability/feature1.h b/clang/test/Modules/Inputs/feature-availability/feature1.h
index dd3556ffa1c5e..66418a8ba6482 100644
--- a/clang/test/Modules/Inputs/feature-availability/feature1.h
+++ b/clang/test/Modules/Inputs/feature-availability/feature1.h
@@ -1,7 +1,7 @@
 #ifndef FEATURE1_H
 #define FEATURE1_H
-#include <feature-availability.h>
+#include <availability_domain.h>
 
-static struct __AvailabilityDomain feature1 __attribute__((availability_domain(feature1))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
+CLANG_ENABLED_AVAILABILITY_DOMAIN(feature1);
 
 #endif
diff --git a/clang/test/Modules/Inputs/feature-availability/feature2.h b/clang/test/Modules/Inputs/feature-availability/feature2.h
index 734b2dd772f78..9d603e03b9954 100644
--- a/clang/test/Modules/Inputs/feature-availability/feature2.h
+++ b/clang/test/Modules/Inputs/feature-availability/feature2.h
@@ -1,8 +1,8 @@
 #ifndef FEATURE2_H
 #define FEATURE2_H
-#include <feature-availability.h>
+#include <availability_domain.h>
 #include "feature1.h"
 
-static struct __AvailabilityDomain feature2 __attribute__((availability_domain(feature2))) = {__AVAILABILITY_DOMAIN_DISABLED, 0};
+CLANG_DISABLED_AVAILABILITY_DOMAIN(feature2);
 
 #endif
diff --git a/clang/test/Modules/feature-availability.c b/clang/test/Modules/feature-availability.c
index 8433a6ab6018a..e21522facc9d7 100644
--- a/clang/test/Modules/feature-availability.c
+++ b/clang/test/Modules/feature-availability.c
@@ -3,14 +3,14 @@
 // RUN: %clang_cc1 -triple arm64-apple-macosx -fmodules -fmodule-file=%t/feature2.pcm -I %S/Inputs/feature-availability -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple arm64-apple-macosx -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -I %S/Inputs/feature-availability -Werror=non-modular-include-in-module -emit-llvm -o - %s | FileCheck %s
 
-#include <feature-availability.h>
+#include <availability_domain.h>
 #include "feature2.h"
 
 #define AVAIL 0
 #define UNAVAIL 1
 
 int pred1(void);
-static struct __AvailabilityDomain feature3 __attribute__((availability_domain(feature3))) = {__AVAILABILITY_DOMAIN_DYNAMIC, pred1};
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(feature3, pred1);
 
 void func0(void);
 __attribute__((availability(domain:feature1, AVAIL))) void func1(void);
diff --git a/clang/test/Sema/feature-availability.c b/clang/test/Sema/feature-availability.c
index dd5bfcac96edd..7ce82e8b0cd5e 100644
--- a/clang/test/Sema/feature-availability.c
+++ b/clang/test/Sema/feature-availability.c
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -triple arm64-apple-macosx15 -fblocks -ffeature-availability=feature1:1 -ffeature-availability=feature2:0 -ffeature-availability=feature3:on -fsyntax-only -Wunreachable-code -verify %s
 // RUN: %clang_cc1 -triple arm64-apple-macosx15 -fblocks -fsyntax-only -Wunreachable-code -verify -DUSE_DOMAIN %s
 
-#include <feature-availability.h>
+#include <availability_domain.h>
 
 #define AVAIL 0
 #define UNAVAIL 1
@@ -9,10 +9,10 @@
 
 #ifdef USE_DOMAIN
 int pred1(void);
-static struct __AvailabilityDomain __feature1 __attribute__((availability_domain(feature1))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
-static struct __AvailabilityDomain __feature2 __attribute__((availability_domain(feature2))) = {__AVAILABILITY_DOMAIN_DISABLED, 0};
-static struct __AvailabilityDomain __feature3 __attribute__((availability_domain(feature3))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
-static struct __AvailabilityDomain __feature4 __attribute__((availability_domain(feature4))) = {__AVAILABILITY_DOMAIN_DYNAMIC, pred1};
+CLANG_ENABLED_AVAILABILITY_DOMAIN(feature1);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(feature2);
+CLANG_ENABLED_AVAILABILITY_DOMAIN(feature3);
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(feature4, pred1);
 #endif
 
 __attribute__((availability(domain:feature1, AVAIL))) void func12(void);
diff --git a/clang/test/SemaObjC/feature-availability.m b/clang/test/SemaObjC/feature-availability.m
index e062c668616b9..6916546eae72c 100644
--- a/clang/test/SemaObjC/feature-availability.m
+++ b/clang/test/SemaObjC/feature-availability.m
@@ -1,15 +1,14 @@
 // RUN: %clang_cc1 -fblocks -ffeature-availability=feature1:ON -ffeature-availability=feature2:OFF -fsyntax-only -verify %s
 // RUN: %clang_cc1 -fblocks -fsyntax-only -verify -DUSE_DOMAIN %s
 
-#include <feature-availability.h>
+#include <availability_domain.h>
 
 #define AVAIL 0
 #define UNAVAIL 1
 
 #ifdef USE_DOMAIN
-int pred1(void);
-static struct __AvailabilityDomain feature1 __attribute__((availability_domain(feature1))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
-static struct __AvailabilityDomain feature2 __attribute__((availability_domain(feature2))) = {__AVAILABILITY_DOMAIN_DISABLED, 0};
+CLANG_ENABLED_AVAILABILITY_DOMAIN(feature1);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(feature2);
 #endif
 
 __attribute__((availability(domain:feature1, AVAIL))) int func1(void);