swiftlang · kavon · Jan 10, 2024 · Jan 10, 2024
diff --git a/clang/lib/Basic/Module.cpp b/clang/lib/Basic/Module.cpp
@@ -308,7 +308,8 @@ bool Module::directlyUses(const Module *Requested) {
   // Anyone is allowed to use our builtin stdarg.h and stddef.h and their
   // accompanying modules.
   if (Requested->getTopLevelModuleName() == "_Builtin_stdarg" ||
-      Requested->getTopLevelModuleName() == "_Builtin_stddef")
+      Requested->getTopLevelModuleName() == "_Builtin_stddef" ||
+      (!Requested->Parent && Requested->Name == "_Builtin_stddef_max_align_t"))
     return true;
 
   if (NoUndeclaredIncludes)

diff --git a/clang/lib/Headers/__stddef_max_align_t.h b/clang/lib/Headers/__stddef_max_align_t.h
@@ -1,4 +1,4 @@
-/*===---- __stddef_max_align_t.h - Definition of max_align_t ---------------===
+/*===---- __stddef_max_align_t.h - Definition of max_align_t for modules ---===
  *
  * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  * See https://llvm.org/LICENSE.txt for license information.

diff --git a/clang/lib/Headers/__stddef_null.h b/clang/lib/Headers/__stddef_null.h
@@ -7,15 +7,7 @@
  *===-----------------------------------------------------------------------===
  */
 
-#if !defined(NULL) || !__has_feature(modules)
-
-/* linux/stddef.h will define NULL to 0. glibc (and other) headers then define
- * __need_NULL and rely on stddef.h to redefine NULL to the correct value again.
- * Modules don't support redefining macros like that, but support that pattern
- * in the non-modules case.
- */
 #undef NULL
-
 #ifdef __cplusplus
 #if !defined(__MINGW32__) && !defined(_MSC_VER)
 #define NULL __null
@@ -25,5 +17,3 @@
 #else
 #define NULL ((void *)0)
 #endif
-
-#endif
diff --git a/clang/lib/Headers/__stddef_nullptr_t.h b/clang/lib/Headers/__stddef_nullptr_t.h
@@ -7,18 +7,19 @@
  *===-----------------------------------------------------------------------===
  */
 
-#ifndef _NULLPTR_T
+#if !defined(_NULLPTR_T) || __has_feature(modules)
+/* Always define nullptr_t when modules are available. */
+#if !__has_feature(modules)
 #define _NULLPTR_T
-
+#endif
 #ifdef __cplusplus
 #if defined(_MSC_EXTENSIONS) && defined(_NATIVE_NULLPTR_SUPPORTED)
 namespace std {
 typedef decltype(nullptr) nullptr_t;
 }
 using ::std::nullptr_t;
 #endif
-#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L
+#else
 typedef typeof(nullptr) nullptr_t;
 #endif
-
 #endif
diff --git a/clang/lib/Headers/__stddef_offsetof.h b/clang/lib/Headers/__stddef_offsetof.h
@@ -7,6 +7,7 @@
  *===-----------------------------------------------------------------------===
  */
 
-#ifndef offsetof
+#if !defined(offsetof) || __has_feature(modules)
+/* Always define offsetof when modules are available. */
 #define offsetof(t, d) __builtin_offsetof(t, d)
 #endif
diff --git a/clang/lib/Headers/__stddef_ptrdiff_t.h b/clang/lib/Headers/__stddef_ptrdiff_t.h
@@ -7,9 +7,10 @@
  *===-----------------------------------------------------------------------===
  */
 
-#ifndef _PTRDIFF_T
+#if !defined(_PTRDIFF_T) || __has_feature(modules)
+/* Always define ptrdiff_t when modules are available. */
+#if !__has_feature(modules)
 #define _PTRDIFF_T
-
+#endif
 typedef __PTRDIFF_TYPE__ ptrdiff_t;
-
 #endif
diff --git a/clang/lib/Headers/__stddef_rsize_t.h b/clang/lib/Headers/__stddef_rsize_t.h
@@ -7,9 +7,10 @@
  *===-----------------------------------------------------------------------===
  */
 
-#ifndef _RSIZE_T
+#if !defined(_RSIZE_T) || __has_feature(modules)
+/* Always define rsize_t when modules are available. */
+#if !__has_feature(modules)
 #define _RSIZE_T
-
+#endif
 typedef __SIZE_TYPE__ rsize_t;
-
 #endif
diff --git a/clang/lib/Headers/__stddef_size_t.h b/clang/lib/Headers/__stddef_size_t.h
@@ -7,9 +7,10 @@
  *===-----------------------------------------------------------------------===
  */
 
-#ifndef _SIZE_T
+#if !defined(_SIZE_T) || __has_feature(modules)
+/* Always define size_t when modules are available. */
+#if !__has_feature(modules)
 #define _SIZE_T
-
+#endif
 typedef __SIZE_TYPE__ size_t;
-
 #endif
diff --git a/clang/lib/Headers/__stddef_unreachable.h b/clang/lib/Headers/__stddef_unreachable.h
@@ -7,6 +7,7 @@
  *===-----------------------------------------------------------------------===
  */
 
-#ifndef unreachable
+#if !defined(unreachable) || __has_feature(modules)
+/* Always define unreachable when modules are available. */
 #define unreachable() __builtin_unreachable()
 #endif
diff --git a/clang/lib/Headers/__stddef_wchar_t.h b/clang/lib/Headers/__stddef_wchar_t.h
@@ -8,16 +8,14 @@
  */
 
 #if !defined(__cplusplus) || (defined(_MSC_VER) && !_NATIVE_WCHAR_T_DEFINED)
-
-#ifndef _WCHAR_T
+/* Always define wchar_t when modules are available. */
+#if !defined(_WCHAR_T) || __has_feature(modules)
+#if !__has_feature(modules)
 #define _WCHAR_T
-
-#ifdef _MSC_EXTENSIONS
+#if defined(_MSC_EXTENSIONS)
 #define _WCHAR_T_DEFINED
 #endif
-
+#endif
 typedef __WCHAR_TYPE__ wchar_t;
-
 #endif
-
 #endif
diff --git a/clang/lib/Headers/__stddef_wint_t.h b/clang/lib/Headers/__stddef_wint_t.h
@@ -7,9 +7,10 @@
  *===-----------------------------------------------------------------------===
  */
 
-#ifndef _WINT_T
+/* Always define wint_t when modules are available. */
+#if !defined(_WINT_T) || __has_feature(modules)
+#if !__has_feature(modules)
 #define _WINT_T
-
+#endif
 typedef __WINT_TYPE__ wint_t;
-
 #endif
diff --git a/clang/lib/Headers/module.modulemap b/clang/lib/Headers/module.modulemap
@@ -153,164 +153,9 @@ module _Builtin_intrinsics [system] [extern_c] {
   }
 }
 
-// Start -fbuiltin-headers-in-system-modules affected modules
-
-// The following modules all ignore their top level headers
-// when -fbuiltin-headers-in-system-modules is passed, and
-// most of those headers join system modules when present.
-
-// e.g. if -fbuiltin-headers-in-system-modules is passed, then
-// float.h will not be in the _Builtin_float module (that module
-// will be empty). If there is a system module that declares
-// `header "float.h"`, then the builtin float.h will join
-// that module. The system float.h (if present) will be treated
-// as a textual header in the sytem module.
-module _Builtin_float [system] {
-  header "float.h"
-  export *
-}
-
-module _Builtin_inttypes [system] {
-  header "inttypes.h"
-  export *
-}
-
-module _Builtin_iso646 [system] {
-  header "iso646.h"
-  export *
-}
-
-module _Builtin_limits [system] {
-  header "limits.h"
-  export *
-}
-
-module _Builtin_stdalign [system] {
-  header "stdalign.h"
-  export *
-}
-
-// When -fbuiltin-headers-in-system-modules is passed, only
-// the top level headers are removed, the implementation headers
-// will always be in their submodules. That means when stdarg.h
-// is included, it will still import this module and make the
-// appropriate submodules visible.
-module _Builtin_stdarg [system] {
-  textual header "stdarg.h"
-
-  explicit module __gnuc_va_list {
-    header "__stdarg___gnuc_va_list.h"
-    export *
-  }
-
-  explicit module __va_copy {
-    header "__stdarg___va_copy.h"
-    export *
-  }
-
-  explicit module va_arg {
-    header "__stdarg_va_arg.h"
-    export *
-  }
-
-  explicit module va_copy {
-    header "__stdarg_va_copy.h"
-    export *
-  }
-
-  explicit module va_list {
-    header "__stdarg_va_list.h"
-    export *
-  }
-}
-
-module _Builtin_stdatomic [system] {
-  header "stdatomic.h"
-  export *
-}
-
-module _Builtin_stdbool [system] {
-  header "stdbool.h"
-  export *
-}
-
-module _Builtin_stddef [system] {
-  textual header "stddef.h"
-
-  explicit module max_align_t {
-    header "__stddef_max_align_t.h"
-    export *
-  }
-
-  explicit module null {
-    header "__stddef_null.h"
-    export *
-  }
-
-  explicit module nullptr_t {
-    header "__stddef_nullptr_t.h"
-    export *
-  }
-
-  explicit module offsetof {
-    header "__stddef_offsetof.h"
-    export *
-  }
-
-  explicit module ptrdiff_t {
-    header "__stddef_ptrdiff_t.h"
-    export *
-  }
-
-  explicit module rsize_t {
-    header "__stddef_rsize_t.h"
-    export *
-  }
-
-  explicit module size_t {
-    header "__stddef_size_t.h"
-    export *
-  }
-
-  explicit module unreachable {
-    header "__stddef_unreachable.h"
-    export *
-  }
-
-  explicit module wchar_t {
-    header "__stddef_wchar_t.h"
-    export *
-  }
-}
-
-/* wint_t is provided by <wchar.h> and not <stddef.h>. It's here
- * for compatibility, but must be explicitly requested. Therefore
- * __stddef_wint_t.h is not part of _Builtin_stddef. */
-module _Builtin_stddef_wint_t [system] {
-  header "__stddef_wint_t.h"
-  export *
-}
-
-module _Builtin_stdint [system] {
-  header "stdint.h"
-  export *
-}
-
-module _Builtin_stdnoreturn [system] {
-  header "stdnoreturn.h"
-  export *
-}
-
-module _Builtin_tgmath [system] {
-  header "tgmath.h"
-  export *
-}
-
-module _Builtin_unwind [system] {
-  header "unwind.h"
-  export *
+module _Builtin_stddef_max_align_t [system] [extern_c] {
+  header "__stddef_max_align_t.h"
 }
-// End -fbuiltin-headers-in-system-modules affected modules
 
 module opencl_c {
   requires opencl

diff --git a/clang/lib/Headers/stdarg.h b/clang/lib/Headers/stdarg.h
@@ -7,31 +7,9 @@
  *===-----------------------------------------------------------------------===
  */
 
-/*
- * This header is designed to be included multiple times. If any of the __need_
- * macros are defined, then only that subset of interfaces are provided. This
- * can be useful for POSIX headers that need to not expose all of stdarg.h, but
- * need to use some of its interfaces. Otherwise this header provides all of
- * the expected interfaces.
- *
- * When clang modules are enabled, this header is a textual header. It ignores
- * its header guard so that multiple submodules can export its interfaces.
- * Take module SM with submodules A and B, whose headers both include stdarg.h
- * When SM.A builds, __STDARG_H will be defined. When SM.B builds, the
- * definition from SM.A will leak when building without local submodule
- * visibility. stdarg.h wouldn't include any of its implementation headers, and
- * SM.B wouldn't import any of the stdarg modules, and SM.B's `export *`
- * wouldn't export any stdarg interfaces as expected. However, since stdarg.h
- * ignores its header guard when building with modules, it all works as
- * expected.
- *
- * When clang modules are not enabled, the header guards can function in the
- * normal simple fashion.
- */
-#if !defined(__STDARG_H) || __has_feature(modules) ||                          \
-    defined(__need___va_list) || defined(__need_va_list) ||                    \
-    defined(__need_va_arg) || defined(__need___va_copy) ||                     \
-    defined(__need_va_copy)
+#if !defined(__STDARG_H) || defined(__need___va_list) ||                       \
+    defined(__need_va_list) || defined(__need_va_arg) ||                       \
+    defined(__need___va_copy) || defined(__need_va_copy)
 
 #if !defined(__need___va_list) && !defined(__need_va_list) &&                  \
     !defined(__need_va_arg) && !defined(__need___va_copy) &&                   \