[libc++][CI] Update to Clang-20

.github/workflows/libcxx-build-and-test.yaml

@@ -38,11 +38,11 @@ env:
   # LLVM POST-BRANCH bump version
   # LLVM POST-BRANCH add compiler test for ToT - 1, e.g. "Clang 17"
   # LLVM RELEASE bump remove compiler ToT - 3, e.g. "Clang 15"
-  LLVM_HEAD_VERSION: "19"   # Used compiler, update POST-BRANCH.
-  LLVM_PREVIOUS_VERSION: "18"
-  LLVM_OLDEST_VERSION: "17"
+  LLVM_HEAD_VERSION: "20"   # Used compiler, update POST-BRANCH.
+  LLVM_PREVIOUS_VERSION: "19"
+  LLVM_OLDEST_VERSION: "18"
   GCC_STABLE_VERSION: "13"
-  LLVM_SYMBOLIZER_PATH: "/usr/bin/llvm-symbolizer-19"
+  LLVM_SYMBOLIZER_PATH: "/usr/bin/llvm-symbolizer-20"
   CLANG_CRASH_DIAGNOSTICS_DIR: "crash_diagnostics"
 
 
@@ -59,8 +59,8 @@ jobs:
           'generic-cxx26',
           'generic-modules'
         ]
-        cc: [  'clang-19' ]
-        cxx: [ 'clang++-19' ]
+        cc: [  'clang-20' ]
+        cxx: [ 'clang++-20' ]
         include:
           - config: 'generic-gcc'
             cc: 'gcc-14'
@@ -97,18 +97,18 @@ jobs:
           'generic-cxx20',
           'generic-cxx23'
         ]
-        cc: [ 'clang-19' ]
-        cxx: [ 'clang++-19' ]
+        cc: [ 'clang-20' ]
+        cxx: [ 'clang++-20' ]
         include:
           - config: 'generic-gcc-cxx11'
             cc: 'gcc-14'
             cxx: 'g++-14'
-          - config: 'generic-cxx23'
-            cc: 'clang-17'
-            cxx: 'clang++-17'
           - config: 'generic-cxx26'
             cc: 'clang-18'
             cxx: 'clang++-18'
+          - config: 'generic-cxx26'
+            cc: 'clang-19'
+            cxx: 'clang++-19'
     steps:
       - uses: actions/checkout@v4
       - name: ${{ matrix.config }}
@@ -179,8 +179,8 @@ jobs:
       - name: ${{ matrix.config }}
         run: libcxx/utils/ci/run-buildbot ${{ matrix.config }}
         env:
-          CC: clang-19
-          CXX: clang++-19
+          CC: clang-20
+          CXX: clang++-20
       - uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 # v4.3.0
         if: always()
         with:

libcxx/docs/ReleaseNotes/20.rst

@@ -64,8 +64,8 @@ Deprecations and Removals
   removed in language modes prior to C++20. If you are using these features prior to C++20, you will need to
   update to ``-std=c++20``.
 
-- TODO: The relational operators for ``std::chrono::weekday`` will be removed entirely, and the
-  ``_LIBCPP_ENABLE_REMOVED_WEEKDAY_RELATIONAL_OPERATORS`` macro that was used to re-enable this extension will be
+- The relational operators for ``std::chrono::weekday`` are removed entirely, and the
+  ``_LIBCPP_ENABLE_REMOVED_WEEKDAY_RELATIONAL_OPERATORS`` macro that was used to re-enable this extension is
   ignored in LLVM 20.
 
 - The ``_LIBCPP_ENABLE_REMOVED_ALLOCATOR_CONST`` macro no longer has any effect. ``std::allocator<const T>`` is not

libcxx/docs/index.rst

@@ -130,7 +130,7 @@ velocity, libc++ drops support for older compilers as newer ones are released.
 ============ =============== ========================== =====================
 Compiler     Versions        Restrictions               Support policy
 ============ =============== ========================== =====================
-Clang        17, 18, 19-git                             latest two stable releases per `LLVM's release page <https://releases.llvm.org>`_ and the development version
+Clang        18, 19, 20-git                             latest two stable releases per `LLVM's release page <https://releases.llvm.org>`_ and the development version
 AppleClang   15                                         latest stable release per `Xcode's release page <https://developer.apple.com/documentation/xcode-release-notes>`_
 Open XL      17.1 (AIX)                                 latest stable release per `Open XL's documentation page <https://www.ibm.com/docs/en/openxl-c-and-cpp-aix>`_
 GCC          14              In C++11 or later only     latest stable release per `GCC's release page <https://gcc.gnu.org/releases.html>`_

libcxx/include/__chrono/weekday.h

@@ -79,25 +79,6 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr bool operator==(const weekday& __lhs, con
   return __lhs.c_encoding() == __rhs.c_encoding();
 }
 
-// TODO(LLVM 20): Remove the escape hatch
-#  ifdef _LIBCPP_ENABLE_REMOVED_WEEKDAY_RELATIONAL_OPERATORS
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator<(const weekday& __lhs, const weekday& __rhs) noexcept {
-  return __lhs.c_encoding() < __rhs.c_encoding();
-}
-
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator>(const weekday& __lhs, const weekday& __rhs) noexcept {
-  return __rhs < __lhs;
-}
-
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator<=(const weekday& __lhs, const weekday& __rhs) noexcept {
-  return !(__rhs < __lhs);
-}
-
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool operator>=(const weekday& __lhs, const weekday& __rhs) noexcept {
-  return !(__lhs < __rhs);
-}
-#  endif // _LIBCPP_ENABLE_REMOVED_WEEKDAY_RELATIONAL_OPERATORS
-
 _LIBCPP_HIDE_FROM_ABI inline constexpr weekday operator+(const weekday& __lhs, const days& __rhs) noexcept {
   auto const __mu = static_cast<long long>(__lhs.c_encoding()) + __rhs.count();
   auto const __yr = (__mu >= 0 ? __mu : __mu - 6) / 7;

libcxx/include/__configuration/compiler.h

@@ -33,8 +33,8 @@
 // Warn if a compiler version is used that is not supported anymore
 // LLVM RELEASE Update the minimum compiler versions
 #  if defined(_LIBCPP_CLANG_VER)
-#    if _LIBCPP_CLANG_VER < 1700
-#      warning "Libc++ only supports Clang 17 and later"
+#    if _LIBCPP_CLANG_VER < 1800
+#      warning "Libc++ only supports Clang 18 and later"
 #    endif
 #  elif defined(_LIBCPP_APPLE_CLANG_VER)
 #    if _LIBCPP_APPLE_CLANG_VER < 1500

libcxx/include/__type_traits/promote.h

@@ -13,20 +13,12 @@
 #include <__type_traits/integral_constant.h>
 #include <__type_traits/is_arithmetic.h>
 
-#if defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER == 1700
-#  include <__type_traits/is_same.h>
-#  include <__utility/declval.h>
-#endif
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-// TODO(LLVM-20): Remove this workaround
-#if !defined(_LIBCPP_CLANG_VER) || _LIBCPP_CLANG_VER != 1700
-
 template <class... _Args>
 class __promote {
   static_assert((is_arithmetic<_Args>::value && ...));
@@ -50,79 +42,6 @@ class __promote {
   using type = decltype((__test(_Args()) + ...));
 };
 
-#else
-
-template <class _Tp>
-struct __numeric_type {
-  static void __test(...);
-  static float __test(float);
-  static double __test(char);
-  static double __test(int);
-  static double __test(unsigned);
-  static double __test(long);
-  static double __test(unsigned long);
-  static double __test(long long);
-  static double __test(unsigned long long);
-#  ifndef _LIBCPP_HAS_NO_INT128
-  static double __test(__int128_t);
-  static double __test(__uint128_t);
-#  endif
-  static double __test(double);
-  static long double __test(long double);
-
-  typedef decltype(__test(std::declval<_Tp>())) type;
-  static const bool value = _IsNotSame<type, void>::value;
-};
-
-template <>
-struct __numeric_type<void> {
-  static const bool value = true;
-};
-
-template <class _A1,
-          class _A2 = void,
-          class _A3 = void,
-          bool      = __numeric_type<_A1>::value && __numeric_type<_A2>::value && __numeric_type<_A3>::value>
-class __promote_imp {
-public:
-  static const bool value = false;
-};
-
-template <class _A1, class _A2, class _A3>
-class __promote_imp<_A1, _A2, _A3, true> {
-private:
-  typedef typename __promote_imp<_A1>::type __type1;
-  typedef typename __promote_imp<_A2>::type __type2;
-  typedef typename __promote_imp<_A3>::type __type3;
-
-public:
-  typedef decltype(__type1() + __type2() + __type3()) type;
-  static const bool value = true;
-};
-
-template <class _A1, class _A2>
-class __promote_imp<_A1, _A2, void, true> {
-private:
-  typedef typename __promote_imp<_A1>::type __type1;
-  typedef typename __promote_imp<_A2>::type __type2;
-
-public:
-  typedef decltype(__type1() + __type2()) type;
-  static const bool value = true;
-};
-
-template <class _A1>
-class __promote_imp<_A1, void, void, true> {
-public:
-  typedef typename __numeric_type<_A1>::type type;
-  static const bool value = true;
-};
-
-template <class _A1, class _A2 = void, class _A3 = void>
-class __promote : public __promote_imp<_A1, _A2, _A3> {};
-
-#endif // !defined(_LIBCPP_CLANG_VER) || _LIBCPP_CLANG_VER >= 1700
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_PROMOTE_H

libcxx/test/libcxx/atomics/diagnose_invalid_memory_order.verify.cpp

@@ -9,7 +9,7 @@
 // This test fails with Clang <18 because diagnose_if doesn't emit all of the
 // diagnostics when -fdelayed-template-parsing is enabled, like it is in MSVC
 // mode.
-// XFAIL: msvc && clang-17
+// XFAIL: msvc
 
 // REQUIRES: diagnose-if-support
 

libcxx/test/libcxx/clang_tidy.gen.py

@@ -18,22 +18,21 @@
 from libcxx.header_information import lit_header_restrictions, public_headers
 
 for header in public_headers:
-  print(f"""\
+    print(
+        f"""\
 //--- {header}.sh.cpp
 
 // REQUIRES: has-clang-tidy
 
 // The GCC compiler flags are not always compatible with clang-tidy.
 // UNSUPPORTED: gcc
 
-// Clang 17 has false positives.
-// UNSUPPORTED: clang-17
-
 {lit_header_restrictions.get(header, '')}
 
 // TODO: run clang-tidy with modules enabled once they are supported
 // RUN: %{{clang-tidy}} %s --warnings-as-errors=* -header-filter=.* --checks='-*,libcpp-*' --load=%{{test-tools-dir}}/clang_tidy_checks/libcxx-tidy.plugin -- %{{compile_flags}} -fno-modules
 // RUN: %{{clang-tidy}} %s --warnings-as-errors=* -header-filter=.* --config-file=%{{libcxx-dir}}/.clang-tidy -- -Wweak-vtables %{{compile_flags}} -fno-modules
 
 #include <{header}>
-""")
+"""
+    )

libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp

@@ -12,7 +12,7 @@
 // UNSUPPORTED: c++03
 
 // TODO: Investigate these failures which break the CI.
-// UNSUPPORTED: clang-17, clang-18, clang-19
+// UNSUPPORTED: clang-18, clang-19
 
 // The Android libc++ tests are run on a non-Android host, connected to an
 // Android device over adb. gdb needs special support to make this work (e.g.

libcxx/test/libcxx/ranges/range.adaptors/range.lazy.split/no_unique_address.compile.pass.cpp

@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// XFAIL: msvc && clang-17
+// XFAIL: msvc
 
 // class lazy_split_view {
 //   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();

libcxx/test/libcxx/ranges/range.adaptors/range.split/no_unique_address.compile.pass.cpp

@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// XFAIL: msvc && clang-17
+// XFAIL: msvc
 
 // class split_view {
 //   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();

libcxx/test/libcxx/ranges/range.factories/range.istream.view/no_unique_address.compile.pass.cpp

@@ -8,7 +8,7 @@
 
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// XFAIL: msvc && clang-17
+// XFAIL: msvc
 
 // Test the libc++ extension that the value stored in `std::ranges::istream_view` has been marked
 // as _LIBCPP_NO_UNIQUE_ADDRESS

libcxx/test/libcxx/utilities/expected/expected.expected/transform_error.mandates.verify.cpp

@@ -6,10 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// Clang-18 fixed some spurious clang diagnostics. Once clang-18 is the
-// minimum required version these obsolete tests can be removed.
-// TODO(LLVM-20) remove spurious clang diagnostic tests.
-
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
 
 // With clang-cl, some warnings have a 'which is a Microsoft extension' suffix
@@ -59,12 +55,12 @@ void test() {
   {
     std::expected<int, int> e;
     e.transform_error(return_unexpected<int&>); // expected-error-re@*:* {{static assertion failed {{.*}}The result of {{.*}} must be a valid template argument for unexpected}}
-    // expected-error-re@*:* 0-1 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
+    // expected-error-re@*:* {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
     // expected-error-re@*:* {{static assertion failed {{.*}}[expected.object.general] A program that instantiates the definition of template expected<T, E> for {{.*}} is ill-formed.}}
     // expected-error-re@*:* 0-1 {{union member {{.*}} has reference type {{.*}}}}
 
     e.transform_error(return_no_object<int&>); // expected-error-re@*:* {{static assertion failed {{.*}}The result of {{.*}} must be a valid template argument for unexpected}}
-    // expected-error-re@*:* 0-1 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
+    // expected-error-re@*:* {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
     // expected-error-re@*:* {{static assertion failed {{.*}}[expected.object.general] A program that instantiates the definition of template expected<T, E> for {{.*}} is ill-formed.}}
     // expected-warning-re@*:* 0-1 {{union member {{.*}} has reference type {{.*}}, which is a Microsoft extension}}
   }
@@ -73,27 +69,27 @@ void test() {
   {
     const std::expected<int, int> e;
     e.transform_error(return_unexpected<const int &>); // expected-error-re@*:* {{static assertion failed {{.*}}The result of {{.*}} must be a valid template argument for unexpected}}
-    // expected-error-re@*:* 0-2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
+    // expected-error-re@*:* 2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
     e.transform_error(return_no_object<const int &>); // expected-error-re@*:* {{static assertion failed {{.*}}The result of {{.*}} must be a valid template argument for unexpected}}
-    // expected-error-re@*:* 0-2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
+    // expected-error-re@*:* 2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
   }
 
   // Test && overload
   {
     std::expected<int, int> e;
     std::move(e).transform_error(return_unexpected<int&&>); // expected-error-re@*:* {{static assertion failed {{.*}}The result of {{.*}} must be a valid template argument for unexpected}}
-    // expected-error-re@*:* 0-2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
+    // expected-error-re@*:* 2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
     std::move(e).transform_error(return_no_object<int&&>); // expected-error-re@*:* {{static assertion failed {{.*}}The result of {{.*}} must be a valid template argument for unexpected}}
-    // expected-error-re@*:* 0-2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
+    // expected-error-re@*:* 2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
   }
 
   // Test const&& overload
   {
     const std::expected<int, int> e;
     std::move(e).transform_error(return_unexpected<const int&&>); // expected-error-re@*:* {{static assertion failed {{.*}}The result of {{.*}} must be a valid template argument for unexpected}}
-    // expected-error-re@*:* 0-2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
+    // expected-error-re@*:* 2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
     std::move(e).transform_error(return_no_object<const int&&>); // expected-error-re@*:* {{static assertion failed {{.*}}The result of {{.*}} must be a valid template argument for unexpected}}
-    // expected-error-re@*:* 0-2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
+    // expected-error-re@*:* 2 {{{{(excess elements in struct initializer|no matching constructor for initialization of)}}{{.*}}}}
   }
 }
 // clang-format on