NFC: Fix duplicate definition of macro warnings.

Centralize the `SWIFT_{BEGIN/END}_NULLABILITY_ANNOTATIONS` definitions in a new
Nullability.h header to share.

Author: tshortli

include/swift/AST/CASTBridging.h

@@ -15,6 +15,7 @@
 
 #include "swift/Basic/CBasicBridging.h"
 #include "swift/Basic/Compiler.h"
+#include "swift/Basic/Nullability.h"
 
 // NOTE: DO NOT #include any stdlib headers here. e.g. <stdint.h>. Those are
 // part of "Darwin"/"Glibc" module, so when a Swift file imports this header,
@@ -488,7 +489,4 @@ _Bool Plugin_waitForNextMessage(PluginHandle handle, BridgedData *data);
 
 SWIFT_END_NULLABILITY_ANNOTATIONS
 
-#undef SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
-#undef SWIFT_END_NULLABILITY_ANNOTATIONS
-
 #endif // SWIFT_C_AST_ASTBRIDGING_H

include/swift/Basic/BridgedSwiftObject.h

@@ -18,6 +18,8 @@
 #ifndef SWIFT_BASIC_BRIDGEDSWIFTOBJECT_H
 #define SWIFT_BASIC_BRIDGEDSWIFTOBJECT_H
 
+#include "swift/Basic/Nullability.h"
+
 #if defined(__OpenBSD__)
 #include <sys/stdint.h>
 #else
@@ -28,28 +30,6 @@
 #define __has_feature(feature) 0
 #endif
 
-// TODO: These macro definitions are duplicated in Visibility.h. Move
-// them to a single file if we find a location that both Visibility.h and
-// BridgedSwiftObject.h can import.
-#if __has_feature(nullability)
-// Provide macros to temporarily suppress warning about the use of
-// _Nullable and _Nonnull.
-#define SWIFT_BEGIN_NULLABILITY_ANNOTATIONS                                   \
-  _Pragma("clang diagnostic push")                                             \
-  _Pragma("clang diagnostic ignored \"-Wnullability-extension\"")
-#define SWIFT_END_NULLABILITY_ANNOTATIONS                                     \
-  _Pragma("clang diagnostic pop")
-
-#else
-// #define _Nullable and _Nonnull to nothing if we're not being built
-// with a compiler that supports them.
-#define _Nullable
-#define _Nonnull
-#define _Null_unspecified
-#define SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
-#define SWIFT_END_NULLABILITY_ANNOTATIONS
-#endif
-
 SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
 
 typedef const void * _Nonnull SwiftMetatype;

include/swift/Basic/CBasicBridging.h

@@ -14,31 +14,19 @@
 #define SWIFT_C_BASIC_BASICBRIDGING_H
 
 #include "swift/Basic/Compiler.h"
+#include "swift/Basic/Nullability.h"
 
 // NOTE: DO NOT #include any stdlib headers here. e.g. <stdint.h>. Those are
 // part of "Darwin"/"Glibc" module, so when a Swift file imports this header,
 // it causes importing the "Darwin"/"Glibc" overlay module. That violates
 // layering. i.e. Darwin overlay is created by Swift compiler.
 
+SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
+
 #if __clang__
-// Provide macros to temporarily suppress warning about the use of
-// _Nullable and _Nonnull.
-#define SWIFT_BEGIN_NULLABILITY_ANNOTATIONS                                    \
-  _Pragma("clang diagnostic push")                                             \
-      _Pragma("clang diagnostic ignored \"-Wnullability-extension\"")          \
-          _Pragma("clang assume_nonnull begin")
-
-#define SWIFT_END_NULLABILITY_ANNOTATIONS                                      \
-  _Pragma("clang diagnostic pop") _Pragma("clang assume_nonnull end")
-#else
-#define SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
-#define SWIFT_END_NULLABILITY_ANNOTATIONS
-#define _Nullable
-#define _Nonnull
+_Pragma("clang assume_nonnull begin")
 #endif
 
-SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
-
 #ifdef __cplusplus
 extern "C" {
 
@@ -119,9 +107,10 @@ void *JSON_array_pushNewValue(void *arrayPtr);
 }
 #endif
 
-SWIFT_END_NULLABILITY_ANNOTATIONS
+#if __clang__
+_Pragma("clang assume_nonnull end")
+#endif
 
-#undef SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
-#undef SWIFT_END_NULLABILITY_ANNOTATIONS
+SWIFT_END_NULLABILITY_ANNOTATIONS
 
 #endif // SWIFT_C_BASIC_BASICBRIDGING_H

include/swift/Basic/Nullability.h

@@ -0,0 +1,37 @@
+//===--- Nullability.h ----------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_BASIC_NULLABILITY_H
+#define SWIFT_BASIC_NULLABILITY_H
+
+// TODO: These macro definitions are duplicated in Visibility.h. Move
+// them to a single file if we find a location that both Visibility.h and
+// BridgedSwiftObject.h can import.
+#if __has_feature(nullability)
+// Provide macros to temporarily suppress warning about the use of
+// _Nullable and _Nonnull.
+#define SWIFT_BEGIN_NULLABILITY_ANNOTATIONS                                    \
+  _Pragma("clang diagnostic push")                                             \
+      _Pragma("clang diagnostic ignored \"-Wnullability-extension\"")
+#define SWIFT_END_NULLABILITY_ANNOTATIONS _Pragma("clang diagnostic pop")
+
+#else
+// #define _Nullable and _Nonnull to nothing if we're not being built
+// with a compiler that supports them.
+#define _Nullable
+#define _Nonnull
+#define _Null_unspecified
+#define SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
+#define SWIFT_END_NULLABILITY_ANNOTATIONS
+#endif
+
+#endif

include/swift/Demangling/Errors.h

@@ -20,7 +20,6 @@
 #define SWIFT_DEMANGLING_ERRORS_H
 
 #include "swift/Demangling/NamespaceMacros.h"
-#include "swift/shims/Visibility.h"
 #include <inttypes.h>
 #include <stdarg.h>
 
@@ -44,6 +43,14 @@
 #endif
 #endif
 
+#ifndef SWIFT_NORETURN
+#if __has_attribute(noreturn)
+#define SWIFT_NORETURN __attribute__((__noreturn__))
+#else
+#define SWIFT_NORETURN
+#endif
+#endif
+
 namespace swift {
 namespace Demangle {
 SWIFT_BEGIN_INLINE_NAMESPACE