[libc++] Remove official Clang 18 support. (#130142)
Since Clang 20 has been release we no longer support Clang 18 per our
policy.
Note the Clang 18 workarounds will be removed in a follow-up patch.
diff --git a/.github/workflows/libcxx-build-and-test.yaml b/.github/workflows/libcxx-build-and-test.yaml
index bb7243a..9b60bc8 100644
--- a/.github/workflows/libcxx-build-and-test.yaml
+++ b/.github/workflows/libcxx-build-and-test.yaml
@@ -100,10 +100,6 @@
- config: 'generic-cxx26'
cc: 'clang-19'
cxx: 'clang++-19'
- # Release transition
- - config: 'generic-cxx23'
- cc: 'clang-18'
- cxx: 'clang++-18'
steps:
- uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
- name: ${{ matrix.config }}
diff --git a/libcxx/docs/index.rst b/libcxx/docs/index.rst
index e2c62e9..a8b0d5c 100644
--- a/libcxx/docs/index.rst
+++ b/libcxx/docs/index.rst
@@ -131,7 +131,7 @@
============ =================== ========================== =====================
Compiler Versions Restrictions Support policy
============ =================== ========================== =====================
-Clang 18, 19, 20, 21-git latest two stable releases per `LLVM's release page <https://releases.llvm.org>`_ and the development version
+Clang 19, 20, 21-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 17.1.3 (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>`_
diff --git a/libcxx/include/__configuration/compiler.h b/libcxx/include/__configuration/compiler.h
index cf459a0..4b6c6cad 100644
--- a/libcxx/include/__configuration/compiler.h
+++ b/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 < 1800
-# warning "Libc++ only supports Clang 18 and later"
+# if _LIBCPP_CLANG_VER < 1900
+# warning "Libc++ only supports Clang 19 and later"
# endif
# elif defined(_LIBCPP_APPLE_CLANG_VER)
# if _LIBCPP_APPLE_CLANG_VER < 1500