[libc++][CMake] Removes LIBCXX_ENABLE_CLANG_TIDY.

[mordante]

The clang-tidy selection in CMake was refactored in #81362. During review it was suggested to remove this CMake option.

[mordante]

@jplehr Can you test whether this patch works correctly on the clang-hip-vega build bots?

[mordante]

@jplehr friendly ping.

[mordante]

@jplehr friendly ping.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Mark de Wever (mordante)

Changes

The clang-tidy selection in CMake was refactored in #81362. During review it was suggested to remove this CMake option.

---

Full diff: https://github.com/llvm/llvm-project/pull/85794.diff

6 Files Affected:

• (modified) libcxx/CMakeLists.txt (-5)
• (modified) libcxx/docs/ReleaseNotes/19.rst (+3)
• (modified) libcxx/test/tools/CMakeLists.txt (+4-8)
• (modified) libcxx/test/tools/clang_tidy_checks/CMakeLists.txt (+41-15)
• (modified) libcxx/utils/ci/buildkite-pipeline.yml (-1)
• (modified) libcxx/utils/ci/run-buildbot (-8)

diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index e565c47c76687a..043d5a8295c1a6 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -123,7 +123,6 @@ option(LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS
    to provide compile-time errors when using features unavailable on some version of
    the shared library they shipped should turn this on and see `include/__availability`
    for more details." OFF)
-option(LIBCXX_ENABLE_CLANG_TIDY "Whether to compile and run clang-tidy checks" OFF)
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-gcc.cfg.in")
@@ -863,10 +862,6 @@ add_subdirectory(modules)
 
 set(LIBCXX_TEST_DEPS "cxx_experimental")
 
-if (LIBCXX_ENABLE_CLANG_TIDY)
-  list(APPEND LIBCXX_TEST_DEPS cxx-tidy)
-endif()
-
 list(APPEND LIBCXX_TEST_DEPS generate-cxx-modules)
 
 if (LIBCXX_INCLUDE_BENCHMARKS)
diff --git a/libcxx/docs/ReleaseNotes/19.rst b/libcxx/docs/ReleaseNotes/19.rst
index 7bc0148c9ff0aa..390de789ddb643 100644
--- a/libcxx/docs/ReleaseNotes/19.rst
+++ b/libcxx/docs/ReleaseNotes/19.rst
@@ -132,3 +132,6 @@ Build System Changes
 
 - The ``LIBCXX_EXECUTOR`` and ``LIBCXXABI_EXECUTOR`` CMake variables have been removed. Please
   set ``LIBCXX_TEST_PARAMS`` to ``executor=<...>`` instead.
+
+- The Cmake variable ``LIBCXX_ENABLE_CLANG_TIDY`` has been removed. The build system has been changed
+  to automatically detect the presence of ``clang-tidy`` and the required ``Clang`` libraries.
diff --git a/libcxx/test/tools/CMakeLists.txt b/libcxx/test/tools/CMakeLists.txt
index e30ad6cdd8201f..6d99c53ad46d9f 100644
--- a/libcxx/test/tools/CMakeLists.txt
+++ b/libcxx/test/tools/CMakeLists.txt
@@ -1,12 +1,8 @@
 
 set(LIBCXX_TEST_TOOLS_PATH ${CMAKE_CURRENT_BINARY_DIR} PARENT_SCOPE)
 
-# TODO: Remove LIBCXX_ENABLE_CLANG_TIDY
-if(LIBCXX_ENABLE_CLANG_TIDY)
-  if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-    message(STATUS "Clang-tidy can only be used when building libc++ with "
-                   "a clang compiler.")
-    return()
-  endif()
-  add_subdirectory(clang_tidy_checks)
+if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  message(STATUS "Clang-tidy tests are disabled due to non-clang based compiler.")
+  return()
 endif()
+add_subdirectory(clang_tidy_checks)
diff --git a/libcxx/test/tools/clang_tidy_checks/CMakeLists.txt b/libcxx/test/tools/clang_tidy_checks/CMakeLists.txt
index 74905a0c3ed1c4..28eed614458336 100644
--- a/libcxx/test/tools/clang_tidy_checks/CMakeLists.txt
+++ b/libcxx/test/tools/clang_tidy_checks/CMakeLists.txt
@@ -9,22 +9,14 @@ set(Clang_DIR_SAVE ${Clang_DIR})
 # versions must match. Otherwise there likely will be ODR-violations. This had
 # led to crashes and incorrect output of the clang-tidy based checks.
 find_package(Clang ${CMAKE_CXX_COMPILER_VERSION})
-
-set(SOURCES
-    abi_tag_on_virtual.cpp
-    header_exportable_declarations.cpp
-    hide_from_abi.cpp
-    proper_version_checks.cpp
-    qualify_declval.cpp
-    robust_against_adl.cpp
-    uglify_attributes.cpp
-
-    libcpp_module.cpp
-   )
-
 if(NOT Clang_FOUND)
-  message(STATUS "Could not find a suitable version of the Clang development package;
-                  custom libc++ clang-tidy checks will not be available.")
+  message(STATUS "Clang-tidy tests are disabled since the "
+                 "Clang development package is unavailable.")
+  return()
+endif()
+if(NOT TARGET clangTidy)
+  message(STATUS "Clang-tidy tests are disabled since the "
+                 "Clang development package has no clangTidy target.")
   return()
 endif()
 
@@ -54,6 +46,38 @@ if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
                         )
 endif()
 
+# In some cases even with the clangTidy target present the headers appear not to
+# be on the system. Run a short test to see whether the header is present.
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/test.cpp" "
+#if !__has_include(\"clang-tidy/ClangTidyCheck.h\")
+  # error No clang-tidy headers
+#endif
+int main(){}
+")
+try_compile(HAS_CLANG_TIDY_HEADERS
+  "${CMAKE_CURRENT_BINARY_DIR}"
+  "${CMAKE_CURRENT_BINARY_DIR}/test.cpp"
+   LINK_LIBRARIES clangTidy)
+
+if(NOT HAS_CLANG_TIDY_HEADERS)
+  message(STATUS "Clang-tidy tests are disabled since the "
+                 "clang-tidy headers are not present.")
+  return()
+endif()
+message(STATUS "Clang-tidy tests are enabled.")
+
+set(SOURCES
+    abi_tag_on_virtual.cpp
+    header_exportable_declarations.cpp
+    hide_from_abi.cpp
+    proper_version_checks.cpp
+    qualify_declval.cpp
+    robust_against_adl.cpp
+    uglify_attributes.cpp
+
+    libcpp_module.cpp
+   )
+
 add_library(cxx-tidy MODULE ${SOURCES})
 target_link_libraries(cxx-tidy clangTidy)
 
@@ -64,3 +88,5 @@ set_target_properties(cxx-tidy PROPERTIES
 
 set_target_properties(cxx-tidy PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 set(CMAKE_SHARED_MODULE_SUFFIX_CXX .plugin) # Use a portable suffix to simplify how we can find it from Lit
+
+list(APPEND LIBCXX_TEST_DEPS cxx-tidy)
diff --git a/libcxx/utils/ci/buildkite-pipeline.yml b/libcxx/utils/ci/buildkite-pipeline.yml
index c43e414418729a..4bacdec8f8d6bc 100644
--- a/libcxx/utils/ci/buildkite-pipeline.yml
+++ b/libcxx/utils/ci/buildkite-pipeline.yml
@@ -43,7 +43,6 @@ definitions:
 
 environment_definitions:
   _common_env: &common_env
-      ENABLE_CLANG_TIDY: "On"
       LLVM_SYMBOLIZER_PATH: "/usr/bin/llvm-symbolizer-${LLVM_HEAD_VERSION}"
       CLANG_CRASH_DIAGNOSTICS_DIR: "crash_diagnostics"
       CC: clang-${LLVM_HEAD_VERSION}
diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
index a6f3eb174308b4..cc72f4639b1a9b 100755
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -44,9 +44,6 @@ CMAKE               The CMake binary to use. This variable is optional.
 CLANG_FORMAT        The clang-format binary to use when generating the format
                     ignore list.
 
-ENABLE_CLANG_TIDY   Whether to compile and run clang-tidy checks. This variable
-                    is optional.
-
 EOF
 }
 
@@ -111,10 +108,6 @@ function clean() {
     rm -rf "${BUILD_DIR}"
 }
 
-if [ -z "${ENABLE_CLANG_TIDY}" ]; then
-    ENABLE_CLANG_TIDY=Off
-fi
-
 function generate-cmake-base() {
     echo "--- Generating CMake"
     ${CMAKE} \
@@ -126,7 +119,6 @@ function generate-cmake-base() {
           -DLIBCXX_ENABLE_WERROR=YES \
           -DLIBCXXABI_ENABLE_WERROR=YES \
           -DLIBUNWIND_ENABLE_WERROR=YES \
-          -DLIBCXX_ENABLE_CLANG_TIDY=${ENABLE_CLANG_TIDY} \
           -DLLVM_LIT_ARGS="-sv --xunit-xml-output test-results.xml --timeout=1500 --time-tests" \
           "${@}"
 }

[mordante]

This was approved and reverted to breakage. This breakage should be addressed, however the original reporter of the breakage has not replied to this PR. Merging it since it blocks other work.