[libc++] Use availability to rely on key functions for bad_expected_access and bad_function_call

ldionne · ldionne · commit 4f8fe85dde06 · 2024-04-02T14:20:06.000-04:00
This patch uses our availability machinery to allow defining a key function
for bad_function_call and bad_expected_access at all times but only rely
on it when we can. This prevents compilers from complaining about weak
vtables and reduces code bloat and the amount of work done by the dynamic
linker.

rdar://111917845
diff --git a/libcxx/include/__availability b/libcxx/include/__availability
@@ -160,6 +160,15 @@
 #  define _LIBCPP_AVAILABILITY_HAS_TZDB 1
 #  define _LIBCPP_AVAILABILITY_TZDB
 
+// These macros determine whether we assume that std::bad_function_call and
+// std::bad_expected_access provide a key function in the dylib. This allows
+// centralizing their vtable and typeinfo instead of having all TUs provide
+// a weak definition that then gets deduplicated.
+#  define _LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION 1
+#  define _LIBCPP_AVAILABILITY_BAD_FUNCTION_CALL_KEY_FUNCTION
+#  define _LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION 1
+#  define _LIBCPP_AVAILABILITY_BAD_EXPECTED_ACCESS_KEY_FUNCTION
+
 #elif defined(__APPLE__)
 
 #  define _LIBCPP_AVAILABILITY_HAS_BAD_OPTIONAL_ACCESS                                                                 \
@@ -290,6 +299,13 @@
 #  else
 #    define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 1
 #  endif
+
+#  define _LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION 0
+#  define _LIBCPP_AVAILABILITY_BAD_FUNCTION_CALL_KEY_FUNCTION __attribute__((unavailable))
+
+#  define _LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION 0
+#  define _LIBCPP_AVAILABILITY_BAD_EXPECTED_ACCESS_KEY_FUNCTION __attribute__((unavailable))
+
 #else
 
 // ...New vendors can add availability markup here...
diff --git a/libcxx/include/__config b/libcxx/include/__config
@@ -120,10 +120,6 @@
 #    define _LIBCPP_ABI_FIX_UNORDERED_NODE_POINTER_UB
 #    define _LIBCPP_ABI_FORWARD_LIST_REMOVE_NODE_POINTER_UB
 #    define _LIBCPP_ABI_FIX_UNORDERED_CONTAINER_SIZE_TYPE
-// Define a key function for `bad_function_call` in the library, to centralize
-// its vtable and typeinfo to libc++ rather than having all other libraries
-// using that class define their own copies.
-#    define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
 // Override the default return value of exception::what() for
 // bad_function_call::what() with a string that is specific to
 // bad_function_call (see http://wg21.link/LWG2233). This is an ABI break
@@ -197,19 +193,6 @@
 #    if defined(__FreeBSD__) && __FreeBSD__ < 14
 #      define _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR
 #    endif
-// For XCOFF linkers, we have problems if we see a weak hidden version of a symbol
-// in user code (like you get with -fvisibility-inlines-hidden) and then a strong def
-// in the library, so we need to always rely on the library version.
-#    if defined(_AIX)
-#      define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
-#    endif
-#  endif
-
-#  if defined(_LIBCPP_BUILDING_LIBRARY) || _LIBCPP_ABI_VERSION >= 2
-// Define a key function for `bad_function_call` in the library, to centralize
-// its vtable and typeinfo to libc++ rather than having all other libraries
-// using that class define their own copies.
-#    define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
 #  endif
 
 // We had some bugs where we use [[no_unique_address]] together with construct_at,
diff --git a/libcxx/include/__expected/bad_expected_access.h b/libcxx/include/__expected/bad_expected_access.h
@@ -9,6 +9,7 @@
 #ifndef _LIBCPP___EXPECTED_BAD_EXPECTED_ACCESS_H
 #define _LIBCPP___EXPECTED_BAD_EXPECTED_ACCESS_H
 
+#include <__availability>
 #include <__config>
 #include <__exception/exception.h>
 #include <__utility/move.h>
@@ -27,6 +28,10 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 template <class _Err>
 class bad_expected_access;
 
+#  if !_LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION
+_LIBCPP_DIAGNOSTIC_PUSH
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wweak-vtables")
+#  endif
 template <>
 class bad_expected_access<void> : public exception {
 protected:
@@ -38,12 +43,15 @@ class bad_expected_access<void> : public exception {
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~bad_expected_access() override                    = default;
 
 public:
-  // The way this has been designed (by using a class template below) means that we'll already
-  // have a profusion of these vtables in TUs, and the dynamic linker will already have a bunch
-  // of work to do. So it is not worth hiding the <void> specialization in the dylib, given that
-  // it adds deployment target restrictions.
+#  if _LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION
+  const char* what() const noexcept override;
+#  else
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL const char* what() const noexcept override { return "bad access to std::expected"; }
+#  endif
 };
+#  if !_LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION
+_LIBCPP_DIAGNOSTIC_POP
+#  endif
 
 template <class _Err>
 class bad_expected_access : public bad_expected_access<void> {
diff --git a/libcxx/include/__functional/function.h b/libcxx/include/__functional/function.h
@@ -11,6 +11,7 @@
 #define _LIBCPP___FUNCTIONAL_FUNCTION_H
 
 #include <__assert>
+#include <__availability>
 #include <__config>
 #include <__exception/exception.h>
 #include <__functional/binary_function.h>
@@ -54,8 +55,10 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 // bad_function_call
 
+#  if !_LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION
 _LIBCPP_DIAGNOSTIC_PUSH
 _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wweak-vtables")
+#  endif
 class _LIBCPP_EXPORTED_FROM_ABI bad_function_call : public exception {
 public:
   _LIBCPP_HIDE_FROM_ABI bad_function_call() _NOEXCEPT                                    = default;
@@ -64,7 +67,7 @@ class _LIBCPP_EXPORTED_FROM_ABI bad_function_call : public exception {
 // Note that when a key function is not used, every translation unit that uses
 // bad_function_call will end up containing a weak definition of the vtable and
 // typeinfo.
-#  ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
+#  if _LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION
   ~bad_function_call() _NOEXCEPT override;
 #  else
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~bad_function_call() _NOEXCEPT override {}
@@ -74,7 +77,9 @@ class _LIBCPP_EXPORTED_FROM_ABI bad_function_call : public exception {
   const char* what() const _NOEXCEPT override;
 #  endif
 };
+#  if !_LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION
 _LIBCPP_DIAGNOSTIC_POP
+#  endif
 
 _LIBCPP_NORETURN inline _LIBCPP_HIDE_FROM_ABI void __throw_bad_function_call() {
 #  ifndef _LIBCPP_HAS_NO_EXCEPTIONS
diff --git a/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -2073,6 +2073,7 @@
 {'is_defined': True, 'name': '__ZTINSt3__117moneypunct_bynameIwLb1EEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__119__shared_weak_countE', 'size': 0, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '__ZTINSt3__119bad_expected_accessIvEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__120__codecvt_utf8_utf16IDiEE', 'size': 0, 'type': 'OBJECT'}
@@ -2264,6 +2265,7 @@
 {'is_defined': True, 'name': '__ZTSNSt3__117moneypunct_bynameIwLb0EEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__117moneypunct_bynameIwLb1EEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '__ZTSNSt3__119bad_expected_accessIvEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__13pmr15memory_resourceE', 'size': 0, 'type': 'OBJECT'}
@@ -2482,6 +2484,7 @@
 {'is_defined': True, 'name': '__ZTVNSt3__117moneypunct_bynameIwLb1EEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__119__shared_weak_countE', 'size': 0, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '__ZTVNSt3__119bad_expected_accessIvEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__120__codecvt_utf8_utf16IDiEE', 'size': 0, 'type': 'OBJECT'}
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
@@ -10,6 +10,7 @@ set(LIBCXX_SOURCES
   chrono.cpp
   error_category.cpp
   exception.cpp
+  expected.cpp
   filesystem/filesystem_clock.cpp
   filesystem/filesystem_error.cpp
   filesystem/path_parser.h
diff --git a/libcxx/src/expected.cpp b/libcxx/src/expected.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <expected>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+const char* bad_expected_access<void>::what() const noexcept { return "bad access to std::expected"; }
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/functional.cpp b/libcxx/src/functional.cpp
@@ -10,9 +10,7 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
 bad_function_call::~bad_function_call() noexcept {}
-#endif
 
 #ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_GOOD_WHAT_MESSAGE
 const char* bad_function_call::what() const noexcept { return "std::bad_function_call"; }
