[libc] Add a .clang-tidy file for the toplevel libc directory.

[sivachandra]

Summary

Generation of the .yaml has been removed to prevent lint from
running with every ninja invocation. The new .clang-tidy file is copied
to the libc build directory so that generated files also get checked.

[michaelrj]

LGTM with nit

libc/.clang-tidy

17–18

nit: this should probably go above VariableIgnoredRegexp for consistency

[sivachandra]

Address comment.

libc/.clang-tidy

-Checks: '-*,llvmlibc-*,readability-identifier-naming'
+InheritParentConfig: false
+Checks: 'readability-identifier-naming'
 HeaderFilterRegex: '.*'
-WarningsAsErrors: 'llvmlibc-*'
 CheckOptions:
-  - key:             llvmlibc-restrict-system-libc-headers.Includes
-    value:           '-*, linux/*, asm/*.h, asm-generic/*.h'
   - key:             readability-identifier-naming.ClassCase
     value:           CamelCase
   - key:             readability-identifier-naming.StructCase
     value:           aNy_CasE
   - key:             readability-identifier-naming.MemberCase
     value:           lower_case
+  - key:             readability-identifier-naming.MemberIgnoredRegexp
+    value:           "^_[A-Za-z0-9_]+$"
   - key:             readability-identifier-naming.VariableCase
     value:           lower_case
   - key:             readability-identifier-naming.VariableIgnoredRegexp
     value:           "^_[A-Za-z0-9_]+$"
   - key:             readability-identifier-naming.FunctionCase
     value:           lower_case
   - key:             readability-identifier-naming.FunctionIgnoredRegexp
     value:           "^_[A-Za-z0-9_]+$"
   - key:             readability-identifier-naming.ConstexprVariableCase
     value:           UPPER_CASE
   - key:             readability-identifier-naming.GetConfigPerFile
     value:           true

libc/CMakeLists.txt

 option(LLVM_LIBC_ENABLE_LINTING "Enables linting of libc source files" OFF)
 if(LLVM_LIBC_ENABLE_LINTING AND (NOT LLVM_LIBC_FULL_BUILD))
   message(FATAL_ERROR "Cannot enable linting when full libc build is not enabled.")
 endif()
 if(LLVM_LIBC_ENABLE_LINTING)
   if("clang-tools-extra" IN_LIST LLVM_ENABLE_PROJECTS
              AND "clang" IN_LIST LLVM_ENABLE_PROJECTS)
     add_custom_target(lint-libc)
-    if(NOT EXISTS "${LIBC_BUILD_DIR}/.clang-tidy")
-      # add a no-op clang tidy file for the build directory so that the tidy 
-      # rules don't attempt to format the generated code.
-      file(WRITE ${LIBC_BUILD_DIR}/.clang-tidy "#InheritParentConfig: false
-      Checks: cppcoreguidelines-avoid-goto")
-    endif()
+    file(COPY ${LIBC_SOURCE_DIR}/.clang-tidy DESTINATION ${LIBC_BUILD_DIR})
   else()
     message(FATAL_ERROR "
       'clang' and 'clang-tools-extra' are required in LLVM_ENABLE_PROJECTS to
       lint llvm-libc. The linting step performs important checks to help prevent
       the introduction of subtle bugs, but it may increase build times.
 
       To disable linting set LLVM_LIBC_ENABLE_LINTING to OFF
       (pass -DLLVM_LIBC_ENABLE_LINTING=OFF to cmake).")

libc/cmake/modules/LLVMLibCObjectRules.cmake

add_custom_command(
       #     Suppressed X warnings (X in non-user code).
       # There seems to be a bug in clang-tidy where by even with --quiet some
       # messages from clang's own diagnostics engine leak through:
       #     X warnings generated.
       # Until this is fixed upstream, we use -fno-caret-diagnostics to surpress
       # these.
       COMMAND $<TARGET_FILE:clang-tidy>
               "--extra-arg=-fno-caret-diagnostics" --quiet
-              "--export-fixes=${CMAKE_CURRENT_BINARY_DIR}/${target_name}.yaml"
               # Path to directory containing compile_commands.json
               -p ${PROJECT_BINARY_DIR}
               ${ADD_ENTRYPOINT_OBJ_SRCS}
       # See above: this might be a second invocation of clang-tidy depending on
       # the conditions above.
       ${restrict_system_headers_check_invocation}
       # We have two options for running commands, add_custom_command and
       # add_custom_target. We don't want to run the linter unless source files
       # have changed. add_custom_target explicitly runs everytime therefore we
       # use add_custom_command. This function requires an output file and since
       # linting doesn't produce a file, we create a dummy file using a
       # crossplatform touch.
       COMMAND "${CMAKE_COMMAND}" -E touch ${lint_timestamp}
       COMMENT "Linting... ${target_name}"
       DEPENDS clang-tidy ${internal_target_name} ${ADD_ENTRYPOINT_OBJ_SRCS}
       WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
-      BYPRODUCTS ${CMAKE_CURRENT_BINARY_DIR}/${target_name}.yaml
     )
 
     add_custom_target(${fq_target_name}.__lint__
       DEPENDS ${lint_timestamp})
     add_dependencies(lint-libc ${fq_target_name}.__lint__)
     add_dependencies(${fq_target_name} ${fq_target_name}.__lint__)
   endif()
 

libc/src/.clang-tidy

+InheritParentConfig: true
 Checks: '-*,llvmlibc-*,readability-identifier-naming'
 HeaderFilterRegex: '.*'
 WarningsAsErrors: 'llvmlibc-*'
 CheckOptions:
   - key:             llvmlibc-restrict-system-libc-headers.Includes
     value:           '-*, linux/*, asm/*.h, asm-generic/*.h'
-  - key:             readability-identifier-naming.ClassCase
-    value:           CamelCase
-  - key:             readability-identifier-naming.StructCase
-    value:           aNy_CasE
-  - key:             readability-identifier-naming.MemberCase
-    value:           lower_case
-  - key:             readability-identifier-naming.VariableCase
-    value:           lower_case
-  - key:             readability-identifier-naming.VariableIgnoredRegexp
-    value:           "^_[A-Za-z0-9_]+$"
-  - key:             readability-identifier-naming.FunctionCase
-    value:           lower_case
-  - key:             readability-identifier-naming.FunctionIgnoredRegexp
-    value:           "^_[A-Za-z0-9_]+$"
-  - key:             readability-identifier-naming.ConstexprVariableCase
-    value:           UPPER_CASE
-  - key:             readability-identifier-naming.GetConfigPerFile
-    value:           true

libc/src/__support/CPP/.clang-tidy

+InheritParentConfig: false
 Checks: '-*,llvmlibc-*'
 HeaderFilterRegex: '.*'
 WarningsAsErrors: 'llvmlibc-*'
 CheckOptions:
   - key:             llvmlibc-restrict-system-libc-headers.Includes
     value:           '-*, linux/*, asm/*.h, asm-generic/*.h'