[libcxx-commits] [libcxx] Revert "[libc++] Allow the use of extensions in the implementation (#79532)" (PR #85792)

Sam McCall via libcxx-commits libcxx-commits at lists.llvm.org
Tue Mar 19 07:08:39 PDT 2024


https://github.com/sam-mccall created https://github.com/llvm/llvm-project/pull/85792

This reverts commit 4d323e404d43526ad8263769f00aace9db2e57c5.

The heavy use of push/pop directives causes a severe compile-time
regression (>50%) when building code that uses libc++ via modules.

See discussion on https://github.com/llvm/llvm-project/pull/79532


>From 233bda0d2d5a4422e7cc296ed0e62730953024b3 Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall at gmail.com>
Date: Tue, 19 Mar 2024 14:59:43 +0100
Subject: [PATCH] Revert "[libc++] Allow the use of extensions in the
 implementation (#79532)"

This reverts commit 4d323e404d43526ad8263769f00aace9db2e57c5.

The heavy use of push/pop directives causes a severe compile-time
regression (>50%) when building code that uses libc++ via modules.

See discussion on https://github.com/llvm/llvm-project/pull/79532
---
 libcxx/include/__config | 61 ++++++++++++++---------------------------
 libcxx/include/tuple    |  6 ++++
 2 files changed, 26 insertions(+), 41 deletions(-)

diff --git a/libcxx/include/__config b/libcxx/include/__config
index 11e13e0c24986a..3a438e85a7b819 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -406,10 +406,6 @@ _LIBCPP_HARDENING_MODE_DEBUG
 #    define __has_include(...) 0
 #  endif
 
-#  ifndef __has_warning
-#    define __has_warning(...) 0
-#  endif
-
 #  if !defined(_LIBCPP_COMPILER_CLANG_BASED) && __cplusplus < 201103L
 #    error "libc++ only supports C++03 with Clang-based compilers. Please enable C++11"
 #  endif
@@ -727,23 +723,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION _LIBCPP_ALWAYS_INLINE
 #  endif
 
-#  ifdef _LIBCPP_COMPILER_CLANG_BASED
-#    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("clang diagnostic push")
-#    define _LIBCPP_DIAGNOSTIC_POP _Pragma("clang diagnostic pop")
-#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str) _Pragma(_LIBCPP_TOSTRING(clang diagnostic ignored str))
-#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
-#  elif defined(_LIBCPP_COMPILER_GCC)
-#    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("GCC diagnostic push")
-#    define _LIBCPP_DIAGNOSTIC_POP _Pragma("GCC diagnostic pop")
-#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str)
-#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str) _Pragma(_LIBCPP_TOSTRING(GCC diagnostic ignored str))
-#  else
-#    define _LIBCPP_DIAGNOSTIC_PUSH
-#    define _LIBCPP_DIAGNOSTIC_POP
-#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str)
-#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
-#  endif
-
 #  if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_FAST
 #    define _LIBCPP_HARDENING_SIG f
 #  elif _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_EXTENSIVE
@@ -831,33 +810,16 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_HIDE_FROM_ABI_AFTER_V1 _LIBCPP_HIDE_FROM_ABI
 #  endif
 
-// TODO: Remove this workaround once we drop support for Clang 16
-#if __has_warning("-Wc++23-extensions")
-#  define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED_CXX23_EXTENSION _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++23-extensions")
-#else
-#  define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED_CXX23_EXTENSION _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++2b-extensions")
-#endif
-
 // Inline namespaces are available in Clang/GCC/MSVC regardless of C++ dialect.
 // clang-format off
-#  define _LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_DIAGNOSTIC_PUSH                                                          \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++11-extensions")                           \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++14-extensions")                           \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++17-extensions")                           \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++20-extensions")                           \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED_CXX23_EXTENSION                                 \
-                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++14-extensions")                             \
-                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++17-extensions")                             \
-                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++20-extensions")                             \
-                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++23-extensions")                             \
-                                      namespace _LIBCPP_TYPE_VISIBILITY_DEFAULT std {                                  \
+#  define _LIBCPP_BEGIN_NAMESPACE_STD namespace _LIBCPP_TYPE_VISIBILITY_DEFAULT std {                                  \
                                inline namespace _LIBCPP_ABI_NAMESPACE {
-#  define _LIBCPP_END_NAMESPACE_STD }} _LIBCPP_DIAGNOSTIC_POP
+#  define _LIBCPP_END_NAMESPACE_STD }}
 
 #  define _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM _LIBCPP_BEGIN_NAMESPACE_STD                                               \
                                              inline namespace __fs { namespace filesystem {
 
-#  define _LIBCPP_END_NAMESPACE_FILESYSTEM }} _LIBCPP_END_NAMESPACE_STD
+#  define _LIBCPP_END_NAMESPACE_FILESYSTEM _LIBCPP_END_NAMESPACE_STD }}
 // clang-format on
 
 #  if __has_attribute(__enable_if__)
@@ -1294,6 +1256,23 @@ __sanitizer_verify_double_ended_contiguous_container(const void*, const void*, c
 // the ABI inconsistent.
 #  endif
 
+#  ifdef _LIBCPP_COMPILER_CLANG_BASED
+#    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("clang diagnostic push")
+#    define _LIBCPP_DIAGNOSTIC_POP _Pragma("clang diagnostic pop")
+#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str) _Pragma(_LIBCPP_TOSTRING(clang diagnostic ignored str))
+#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
+#  elif defined(_LIBCPP_COMPILER_GCC)
+#    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("GCC diagnostic push")
+#    define _LIBCPP_DIAGNOSTIC_POP _Pragma("GCC diagnostic pop")
+#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str)
+#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str) _Pragma(_LIBCPP_TOSTRING(GCC diagnostic ignored str))
+#  else
+#    define _LIBCPP_DIAGNOSTIC_PUSH
+#    define _LIBCPP_DIAGNOSTIC_POP
+#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str)
+#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
+#  endif
+
 // c8rtomb() and mbrtoc8() were added in C++20 and C23. Support for these
 // functions is gradually being added to existing C libraries. The conditions
 // below check for known C library versions and conditions under which these
diff --git a/libcxx/include/tuple b/libcxx/include/tuple
index f78db061b844b0..8e38dfe4d0eaa8 100644
--- a/libcxx/include/tuple
+++ b/libcxx/include/tuple
@@ -540,6 +540,10 @@ class _LIBCPP_TEMPLATE_VIS tuple {
 public:
   // [tuple.cnstr]
 
+  _LIBCPP_DIAGNOSTIC_PUSH
+  _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++20-extensions")
+  _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++20-extensions")
+
   // tuple() constructors (including allocator_arg_t variants)
   template <template <class...> class _IsImpDefault                = __is_implicitly_default_constructible,
             template <class...> class _IsDefault                   = is_default_constructible,
@@ -821,6 +825,8 @@ public:
       : __base_(allocator_arg_t(), __alloc, std::move(__p)) {}
 #  endif // _LIBCPP_STD_VER >= 23
 
+  _LIBCPP_DIAGNOSTIC_POP
+
   // [tuple.assign]
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 tuple&
   operator=(_If<_And<is_copy_assignable<_Tp>...>::value, tuple, __nat> const& __tuple)



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