#===============================================================================
# Setup Project
#===============================================================================
cmake_minimum_required(VERSION 3.20.0)
set(LLVM_SUBPROJECT_TITLE "libc++")

set(LLVM_COMMON_CMAKE_UTILS "${CMAKE_CURRENT_SOURCE_DIR}/../cmake")

# Add path for custom modules
list(INSERT CMAKE_MODULE_PATH 0
  "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
  "${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules"
  "${CMAKE_CURRENT_SOURCE_DIR}/../runtimes/cmake/Modules"
  "${LLVM_COMMON_CMAKE_UTILS}"
  "${LLVM_COMMON_CMAKE_UTILS}/Modules"
  )

set(CMAKE_FOLDER "libc++")

set(LIBCXX_SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR})
set(LIBCXX_BINARY_DIR  ${CMAKE_CURRENT_BINARY_DIR})

include(GNUInstallDirs)
include(WarningFlags)

# Require out of source build.
include(MacroEnsureOutOfSourceBuild)
MACRO_ENSURE_OUT_OF_SOURCE_BUILD(
 "${PROJECT_NAME} requires an out of source build. Please create a separate
 build directory and run 'cmake /path/to/${PROJECT_NAME} [options]' there."
 )
if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND "${CMAKE_CXX_SIMULATE_ID}" STREQUAL "MSVC")
  message(STATUS "Configuring for clang-cl")
  set(LIBCXX_TARGETING_CLANG_CL ON)
endif()

if (MSVC)
  message(STATUS "Configuring for MSVC")
endif()

#===============================================================================
# Setup CMake Options
#===============================================================================
include(CMakeDependentOption)
include(HandleCompilerRT)

# Basic options ---------------------------------------------------------------
option(LIBCXX_ENABLE_SHARED "Build libc++ as a shared library." ON)
option(LIBCXX_ENABLE_STATIC "Build libc++ as a static library." ON)
option(LIBCXX_ENABLE_EXCEPTIONS "Enable exceptions in the built library." ON)
option(LIBCXX_ENABLE_RTTI
  "Use runtime type information.
  This option may only be set to OFF when LIBCXX_ENABLE_EXCEPTIONS=OFF." ON)
option(LIBCXX_ENABLE_FILESYSTEM
  "Whether to include support for parts of the library that rely on a filesystem being
   available on the platform. This includes things like most parts of <filesystem> and
   others like <fstream>" ON)
option(LIBCXX_INCLUDE_TESTS "Build the libc++ tests." ${LLVM_INCLUDE_TESTS})
set(LIBCXX_SUPPORTED_HARDENING_MODES none fast extensive debug)
set(LIBCXX_HARDENING_MODE "none" CACHE STRING
  "Specify the default hardening mode to use. This mode will be used inside the
   compiled library and will be the default when compiling user code. Note that
   users can override this setting in their own code. This does not affect the
   ABI. Supported values are ${LIBCXX_SUPPORTED_HARDENING_MODES}.")
if (NOT "${LIBCXX_HARDENING_MODE}" IN_LIST LIBCXX_SUPPORTED_HARDENING_MODES)
  message(FATAL_ERROR
    "Unsupported hardening mode: '${LIBCXX_HARDENING_MODE}'. Supported values are ${LIBCXX_SUPPORTED_HARDENING_MODES}.")
endif()
set(LIBCXX_ASSERTION_HANDLER_FILE
  "vendor/llvm/default_assertion_handler.in"
  CACHE STRING
  "Specify the path to a header that contains a custom implementation of the
   assertion handler that gets invoked when a hardening assertion fails. If
   provided, this header will be included by the library, replacing the
   default assertion handler. If this is specified as a relative path, it
   is assumed to be relative to '<monorepo>/libcxx'.")
if (NOT IS_ABSOLUTE "${LIBCXX_ASSERTION_HANDLER_FILE}")
  set(LIBCXX_ASSERTION_HANDLER_FILE "${CMAKE_CURRENT_SOURCE_DIR}/${LIBCXX_ASSERTION_HANDLER_FILE}")
endif()
option(LIBCXX_ENABLE_RANDOM_DEVICE
  "Whether to include support for std::random_device in the library. Disabling
   this can be useful when building the library for platforms that don't have
   a source of randomness, such as some embedded platforms. When this is not
   supported, most of <random> will still be available, but std::random_device
   will not." ON)
option(LIBCXX_ENABLE_LOCALIZATION
  "Whether to include support for localization in the library. Disabling
   localization can be useful when porting to platforms that don't support
   the C locale API (e.g. embedded). When localization is not supported,
   several parts of the library will be disabled: <iostream>, <regex>, <locale>
   will be completely unusable, and other parts may be only partly available." ON)
option(LIBCXX_ENABLE_UNICODE
  "Whether to include support for Unicode in the library. Disabling Unicode can
   be useful when porting to platforms that don't support UTF-8 encoding (e.g.
   embedded)." ON)
option(LIBCXX_HAS_TERMINAL_AVAILABLE
  "Build libc++ with support for checking whether a stream is a terminal." ON)
option(LIBCXX_ENABLE_WIDE_CHARACTERS
  "Whether to include support for wide characters in the library. Disabling
   wide character support can be useful when porting to platforms that don't
   support the C functionality for wide characters. When wide characters are
   not supported, several parts of the library will be disabled, notably the
   wide character specializations of std::basic_string." ON)
option(LIBCXX_ENABLE_THREADS "Build libc++ with support for threads." ON)
option(LIBCXX_ENABLE_MONOTONIC_CLOCK
  "Build libc++ with support for a monotonic clock.
  This option may only be set to OFF when LIBCXX_ENABLE_THREADS=OFF." ON)

# To use time zone support in libc++ the platform needs to have the IANA
# database installed. Libc++ will fail to build if this is enabled on a
# platform that does not provide the IANA database. The default is set to the
# current implementation state on the different platforms.
#
# TODO TZDB make the default always ON when most platforms ship with the IANA
# database.
if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
  set(ENABLE_TIME_ZONE_DATABASE_DEFAULT ON)
else()
  set(ENABLE_TIME_ZONE_DATABASE_DEFAULT OFF)
endif()
option(LIBCXX_ENABLE_TIME_ZONE_DATABASE
  "Whether to include support for time zones in the library. Disabling
  time zone support can be useful when porting to platforms that don't
  ship the IANA time zone database. When time zones are not supported,
  time zone support in <chrono> will be disabled." ${ENABLE_TIME_ZONE_DATABASE_DEFAULT})
option(LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS
  "Whether to turn on vendor availability annotations on declarations that depend
   on definitions in a shared library. By default, we assume that we're not building
   libc++ for any specific vendor, and we disable those annotations. Vendors wishing
   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/__configuration/availability.h`
   for more details." OFF)

if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
  set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-gcc.cfg.in")
elseif(MINGW)
  set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-mingw.cfg.in")
elseif(WIN32) # clang-cl
  if (LIBCXX_ENABLE_SHARED)
    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-clangcl.cfg.in")
  else()
    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-static-clangcl.cfg.in")
  endif()
else()
  if (LIBCXX_ENABLE_SHARED)
    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared.cfg.in")
  else()
    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-static.cfg.in")
  endif()
endif()
set(LIBCXX_TEST_CONFIG "${LIBCXX_DEFAULT_TEST_CONFIG}" CACHE STRING
    "The path to the Lit testing configuration to use when running the tests.
     If a relative path is provided, it is assumed to be relative to '<monorepo>/libcxx/test/configs'.")
if (NOT IS_ABSOLUTE "${LIBCXX_TEST_CONFIG}")
  set(LIBCXX_TEST_CONFIG "${CMAKE_CURRENT_SOURCE_DIR}/test/configs/${LIBCXX_TEST_CONFIG}")
endif()
message(STATUS "Using libc++ testing configuration: ${LIBCXX_TEST_CONFIG}")
set(LIBCXX_TEST_PARAMS "" CACHE STRING
    "A list of parameters to run the Lit test suite with.")

# TODO: Figure out how to build GoogleBenchmark on those platforms, and how to build when exceptions or RTTI is disabled
if (WIN32 OR MINGW OR ANDROID OR ${CMAKE_SYSTEM_NAME} MATCHES "AIX"
    OR NOT LIBCXX_ENABLE_LOCALIZATION
    OR NOT LIBCXX_ENABLE_THREADS
    OR NOT LIBCXX_ENABLE_FILESYSTEM
    OR NOT LIBCXX_ENABLE_RANDOM_DEVICE
    OR NOT LIBCXX_ENABLE_EXCEPTIONS
    OR NOT LIBCXX_ENABLE_RTTI)
  set(_include_benchmarks OFF)
else()
  set(_include_benchmarks ON)
endif()
option(LIBCXX_INCLUDE_BENCHMARKS "Build the libc++ benchmarks and their dependencies" ${_include_benchmarks})

option(LIBCXX_INCLUDE_DOCS "Build the libc++ documentation." ${LLVM_INCLUDE_DOCS})
set(LIBCXX_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING
    "Define suffix of library directory name (32/64)")
option(LIBCXX_INSTALL_HEADERS "Install the libc++ headers." ON)
option(LIBCXX_INSTALL_LIBRARY "Install the libc++ library." ON)
option(LIBCXX_INSTALL_MODULES
  "Install the libc++ C++20 module source files (experimental)." ON
)
cmake_dependent_option(LIBCXX_INSTALL_STATIC_LIBRARY
  "Install the static libc++ library." ON
  "LIBCXX_ENABLE_STATIC;LIBCXX_INSTALL_LIBRARY" OFF)
cmake_dependent_option(LIBCXX_INSTALL_SHARED_LIBRARY
  "Install the shared libc++ library." ON
  "LIBCXX_ENABLE_SHARED;LIBCXX_INSTALL_LIBRARY" OFF)

option(LIBCXX_ABI_UNSTABLE "Use the unstable ABI of libc++. This is equivalent to specifying LIBCXX_ABI_VERSION=n, where n is the not-yet-stable version." OFF)
if (LIBCXX_ABI_UNSTABLE)
  set(abi_version "2")
else()
  set(abi_version "1")
endif()
set(LIBCXX_ABI_VERSION "${abi_version}" CACHE STRING
  "ABI version of libc++. Can be either 1 or 2, where 2 is currently the unstable ABI.
   Defaults to 1 unless LIBCXX_ABI_UNSTABLE is specified, in which case this is 2.")
set(LIBCXX_LIBRARY_VERSION "${LIBCXX_ABI_VERSION}.0" CACHE STRING
  "Version of libc++. This will be reflected in the name of the shared library produced.
   For example, -DLIBCXX_LIBRARY_VERSION=x.y will result in the library being named
   libc++.x.y.dylib, along with the usual symlinks pointing to that. On Apple platforms,
   this also controls the linker's 'current_version' property.")
set(LIBCXX_ABI_NAMESPACE "__${LIBCXX_ABI_VERSION}" CACHE STRING "The inline ABI namespace used by libc++. It defaults to __n where `n` is the current ABI version.")
if (NOT LIBCXX_ABI_NAMESPACE MATCHES "__.*")
  message(FATAL_ERROR "LIBCXX_ABI_NAMESPACE must be a reserved identifier, got '${LIBCXX_ABI_NAMESPACE}'.")
endif()
option(LIBCXX_ABI_FORCE_ITANIUM "Ignore auto-detection and force use of the Itanium ABI.")
option(LIBCXX_ABI_FORCE_MICROSOFT "Ignore auto-detection and force use of the Microsoft ABI.")

set(LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION "default" CACHE STRING
  "Override the implementation to use for comparing typeinfos. By default, this
   is detected automatically by the library, but this option allows overriding
   which implementation is used unconditionally.

   See the documentation in <libcxx/include/typeinfo> for details on what each
   value means.")
set(TYPEINFO_COMPARISON_VALUES "default;1;2;3")
if (NOT ("${LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION}" IN_LIST TYPEINFO_COMPARISON_VALUES))
  message(FATAL_ERROR "Value '${LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION}' is not a valid value for
                       LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION")
endif()

set(LIBCXX_ABI_DEFINES "" CACHE STRING "A semicolon separated list of ABI macros to define in the site config header.")
set(LIBCXX_EXTRA_SITE_DEFINES "" CACHE STRING "Extra defines to add into __config_site")
option(LIBCXX_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)

# ABI Library options ---------------------------------------------------------
if (MSVC)
  set(LIBCXX_DEFAULT_ABI_LIBRARY "vcruntime")
else()
  set(LIBCXX_DEFAULT_ABI_LIBRARY "libcxxabi")
endif()

set(LIBCXX_SUPPORTED_ABI_LIBRARIES none libcxxabi system-libcxxabi libcxxrt libstdc++ libsupc++ vcruntime)
set(LIBCXX_CXX_ABI "${LIBCXX_DEFAULT_ABI_LIBRARY}" CACHE STRING "Specify C++ ABI library to use. Supported values are ${LIBCXX_SUPPORTED_ABI_LIBRARIES}.")
if (NOT "${LIBCXX_CXX_ABI}" IN_LIST LIBCXX_SUPPORTED_ABI_LIBRARIES)
  message(FATAL_ERROR "Unsupported C++ ABI library: '${LIBCXX_CXX_ABI}'. Supported values are ${LIBCXX_SUPPORTED_ABI_LIBRARIES}.")
endif()

option(LIBCXX_ENABLE_STATIC_ABI_LIBRARY
  "Use a static copy of the ABI library when linking libc++.
   This option cannot be used with LIBCXX_ENABLE_ABI_LINKER_SCRIPT." OFF)

option(LIBCXX_STATICALLY_LINK_ABI_IN_STATIC_LIBRARY
  "Statically link the ABI library to static library"
  ${LIBCXX_ENABLE_STATIC_ABI_LIBRARY})

option(LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY
  "Statically link the ABI library to shared library"
  ${LIBCXX_ENABLE_STATIC_ABI_LIBRARY})

# Generate and install a linker script inplace of libc++.so. The linker script
# will link libc++ to the correct ABI library. This option is on by default
# on UNIX platforms other than Apple, and on the Fuchsia platform unless we
# statically link libc++abi inside libc++.so, we don't build libc++.so at all
# or we don't have any ABI library.
if (LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY
    OR NOT LIBCXX_ENABLE_SHARED
    OR LIBCXX_CXX_ABI STREQUAL "none")
  set(ENABLE_LINKER_SCRIPT_DEFAULT_VALUE OFF)
elseif((UNIX OR FUCHSIA) AND NOT APPLE)
  set(ENABLE_LINKER_SCRIPT_DEFAULT_VALUE ON)
else()
  set(ENABLE_LINKER_SCRIPT_DEFAULT_VALUE OFF)
endif()
option(LIBCXX_ENABLE_ABI_LINKER_SCRIPT
      "Use and install a linker script for the given ABI library"
      ${ENABLE_LINKER_SCRIPT_DEFAULT_VALUE})

option(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS
  "Build libc++ with definitions for operator new/delete. These are normally
   defined in libc++abi, but this option can be used to define them in libc++
   instead. If you define them in libc++, make sure they are NOT defined in
   libc++abi. Doing otherwise is an ODR violation." OFF)
# Build libc++abi with libunwind. We need this option to determine whether to
# link with libunwind or libgcc_s while running the test cases.
option(LIBCXXABI_USE_LLVM_UNWINDER "Build and use the LLVM unwinder." ON)

# Target options --------------------------------------------------------------
option(LIBCXX_BUILD_32_BITS "Build 32 bit multilib libc++. This option is not supported anymore when building the runtimes. Please specify a full triple instead." ${LLVM_BUILD_32_BITS})
if (LIBCXX_BUILD_32_BITS)
  message(FATAL_ERROR "LIBCXX_BUILD_32_BITS is not supported anymore when building the runtimes, please specify a full triple instead.")
endif()

# Feature options -------------------------------------------------------------
option(LIBCXX_HAS_MUSL_LIBC "Build libc++ with support for the Musl C library" OFF)
option(LIBCXX_HAS_PTHREAD_API "Ignore auto-detection and force use of pthread API" OFF)
option(LIBCXX_HAS_WIN32_THREAD_API "Ignore auto-detection and force use of win32 thread API" OFF)
option(LIBCXX_HAS_EXTERNAL_THREAD_API
  "Build libc++ with an externalized threading API.
   This option may only be set to ON when LIBCXX_ENABLE_THREADS=ON." OFF)

if (LIBCXX_ENABLE_THREADS)
  set(LIBCXX_PSTL_BACKEND "std_thread" CACHE STRING "Which PSTL backend to use")
else()
  set(LIBCXX_PSTL_BACKEND "serial" CACHE STRING "Which PSTL backend to use")
endif()

# Misc options ----------------------------------------------------------------
# FIXME: Turn -pedantic back ON. It is currently off because it warns
# about #include_next which is used everywhere.
option(LIBCXX_ENABLE_PEDANTIC "Compile with pedantic enabled." OFF)
option(LIBCXX_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)

set(LIBCXX_HERMETIC_STATIC_LIBRARY_DEFAULT OFF)
if (WIN32)
  set(LIBCXX_HERMETIC_STATIC_LIBRARY_DEFAULT ON)
endif()
option(LIBCXX_HERMETIC_STATIC_LIBRARY
  "Do not export any symbols from the static library." ${LIBCXX_HERMETIC_STATIC_LIBRARY_DEFAULT})

#===============================================================================
# Check option configurations
#===============================================================================

# Ensure LIBCXX_ENABLE_MONOTONIC_CLOCK is set to ON only when
# LIBCXX_ENABLE_THREADS is on.
if(LIBCXX_ENABLE_THREADS AND NOT LIBCXX_ENABLE_MONOTONIC_CLOCK)
  message(FATAL_ERROR "LIBCXX_ENABLE_MONOTONIC_CLOCK can only be set to OFF"
                      " when LIBCXX_ENABLE_THREADS is also set to OFF.")
endif()

if(NOT LIBCXX_ENABLE_THREADS)
  if(LIBCXX_HAS_PTHREAD_API)
    message(FATAL_ERROR "LIBCXX_HAS_PTHREAD_API can only be set to ON"
                        " when LIBCXX_ENABLE_THREADS is also set to ON.")
  endif()
  if(LIBCXX_HAS_EXTERNAL_THREAD_API)
    message(FATAL_ERROR "LIBCXX_HAS_EXTERNAL_THREAD_API can only be set to ON"
                        " when LIBCXX_ENABLE_THREADS is also set to ON.")
  endif()
  if (LIBCXX_HAS_WIN32_THREAD_API)
    message(FATAL_ERROR "LIBCXX_HAS_WIN32_THREAD_API can only be set to ON"
                        " when LIBCXX_ENABLE_THREADS is also set to ON.")
  endif()

endif()

if (LIBCXX_HAS_EXTERNAL_THREAD_API)
  if (LIBCXX_HAS_PTHREAD_API)
    message(FATAL_ERROR "The options LIBCXX_HAS_EXTERNAL_THREAD_API"
                        " and LIBCXX_HAS_PTHREAD_API cannot be both"
                        " set to ON at the same time.")
  endif()
  if (LIBCXX_HAS_WIN32_THREAD_API)
    message(FATAL_ERROR "The options LIBCXX_HAS_EXTERNAL_THREAD_API"
                        " and LIBCXX_HAS_WIN32_THREAD_API cannot be both"
                        " set to ON at the same time.")
  endif()
endif()

if (LIBCXX_HAS_PTHREAD_API)
  if (LIBCXX_HAS_WIN32_THREAD_API)
    message(FATAL_ERROR "The options LIBCXX_HAS_PTHREAD_API"
                        " and LIBCXX_HAS_WIN32_THREAD_API cannot be both"
                        " set to ON at the same time.")
  endif()
endif()

if (NOT LIBCXX_ENABLE_RTTI AND LIBCXX_ENABLE_EXCEPTIONS)
  message(FATAL_ERROR "Libc++ cannot be built with exceptions enabled but RTTI"
                      " disabled, since that configuration is broken. See"
                      " https://github.com/llvm/llvm-project/issues/66117"
                      " for details.")
endif()

if (LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
    if (APPLE)
      message(FATAL_ERROR "LIBCXX_ENABLE_ABI_LINKER_SCRIPT cannot be used on APPLE targets")
    endif()
    if (NOT LIBCXX_ENABLE_SHARED)
      message(FATAL_ERROR "LIBCXX_ENABLE_ABI_LINKER_SCRIPT is only available for shared library builds.")
    endif()
endif()

if (LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY AND LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
    message(FATAL_ERROR "Conflicting options given.
        LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY cannot be specified with
        LIBCXX_ENABLE_ABI_LINKER_SCRIPT")
endif()

if (LIBCXX_ABI_FORCE_ITANIUM AND LIBCXX_ABI_FORCE_MICROSOFT)
  message(FATAL_ERROR "Only one of LIBCXX_ABI_FORCE_ITANIUM and LIBCXX_ABI_FORCE_MICROSOFT can be specified.")
endif ()

if (LIBCXX_ENABLE_SHARED AND CMAKE_MSVC_RUNTIME_LIBRARY AND
    (NOT CMAKE_MSVC_RUNTIME_LIBRARY MATCHES "DLL$"))
  message(WARNING "A static CRT linked into a shared libc++ doesn't work correctly.")
endif()

#===============================================================================
# Configure System
#===============================================================================

# TODO: Projects that depend on libc++ should use LIBCXX_GENERATED_INCLUDE_DIR
# instead of hard-coding include/c++/v1.

set(LIBCXX_INSTALL_INCLUDE_DIR "${CMAKE_INSTALL_INCLUDEDIR}/c++/v1" CACHE STRING
    "Path where target-agnostic libc++ headers should be installed.")
set(LIBCXX_INSTALL_RUNTIME_DIR "${CMAKE_INSTALL_BINDIR}" CACHE STRING
    "Path where built libc++ runtime libraries should be installed.")
set(LIBCXX_INSTALL_MODULES_DIR "share/libc++/v1" CACHE STRING
    "Path where target-agnostic libc++ module source files should be installed.")

set(LIBCXX_SHARED_OUTPUT_NAME "c++" CACHE STRING "Output name for the shared libc++ runtime library.")
set(LIBCXX_STATIC_OUTPUT_NAME "c++" CACHE STRING "Output name for the static libc++ runtime library.")

if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
  set(LIBCXX_TARGET_SUBDIR ${LLVM_DEFAULT_TARGET_TRIPLE})
  if(LIBCXX_LIBDIR_SUBDIR)
    string(APPEND LIBCXX_TARGET_SUBDIR /${LIBCXX_LIBDIR_SUBDIR})
  endif()
  cmake_path(NORMAL_PATH LIBCXX_TARGET_SUBDIR)
  set(LIBCXX_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LIBCXX_TARGET_SUBDIR})
  set(LIBCXX_GENERATED_INCLUDE_DIR "${LLVM_BINARY_DIR}/include/c++/v1")
  set(LIBCXX_GENERATED_MODULE_DIR "${LLVM_BINARY_DIR}/modules/c++/v1")
  set(LIBCXX_GENERATED_INCLUDE_TARGET_DIR "${LLVM_BINARY_DIR}/include/${LIBCXX_TARGET_SUBDIR}/c++/v1")
  set(LIBCXX_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LIBCXX_TARGET_SUBDIR} CACHE STRING
      "Path where built libc++ libraries should be installed.")
  set(LIBCXX_INSTALL_INCLUDE_TARGET_DIR "${CMAKE_INSTALL_INCLUDEDIR}/${LIBCXX_TARGET_SUBDIR}/c++/v1" CACHE STRING
      "Path where target-specific libc++ headers should be installed.")
  unset(LIBCXX_TARGET_SUBDIR)
else()
  if(LLVM_LIBRARY_OUTPUT_INTDIR)
    set(LIBCXX_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
    set(LIBCXX_GENERATED_INCLUDE_DIR "${LLVM_BINARY_DIR}/include/c++/v1")
    set(LIBCXX_GENERATED_MODULE_DIR "${LLVM_BINARY_DIR}/modules/c++/v1")
  else()
    set(LIBCXX_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LIBCXX_LIBDIR_SUFFIX})
    set(LIBCXX_GENERATED_INCLUDE_DIR "${CMAKE_BINARY_DIR}/include/c++/v1")
    set(LIBCXX_GENERATED_MODULE_DIR "${CMAKE_BINARY_DIR}/modules/c++/v1")
  endif()
  set(LIBCXX_GENERATED_INCLUDE_TARGET_DIR "${LIBCXX_GENERATED_INCLUDE_DIR}")
  set(LIBCXX_INSTALL_LIBRARY_DIR lib${LIBCXX_LIBDIR_SUFFIX} CACHE STRING
      "Path where built libc++ libraries should be installed.")
  set(LIBCXX_INSTALL_INCLUDE_TARGET_DIR "${LIBCXX_INSTALL_INCLUDE_DIR}" CACHE STRING
      "Path where target-specific libc++ headers should be installed.")
endif()

set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${LIBCXX_LIBRARY_DIR})
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${LIBCXX_LIBRARY_DIR})
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${LIBCXX_LIBRARY_DIR})

# Declare libc++ configuration variables.
# They are intended for use as follows:
# LIBCXX_CXX_FLAGS: General flags for both the compiler and linker.
# LIBCXX_COMPILE_FLAGS: Compile only flags.
# LIBCXX_LINK_FLAGS: Linker only flags.
# LIBCXX_LIBRARIES: libraries libc++ is linked to.
set(LIBCXX_COMPILE_FLAGS "")
set(LIBCXX_LINK_FLAGS "")
set(LIBCXX_LIBRARIES "")
set(LIBCXX_ADDITIONAL_COMPILE_FLAGS "" CACHE STRING
    "Additional compile flags to use when building libc++. This should be a CMake ;-delimited list of individual
     compiler options to use. For options that must be passed as-is to the compiler without deduplication (e.g.
     `-Xclang -foo` option groups), consider using `SHELL:` (https://cmake.org/cmake/help/latest/command/add_compile_options.html#option-de-duplication).")
set(LIBCXX_ADDITIONAL_LIBRARIES "" CACHE STRING
    "Additional libraries libc++ is linked to which can be provided in cache")

# Include macros for adding and removing libc++ flags.
include(HandleLibcxxFlags)

# Target flags ================================================================
# These flags get added to CMAKE_CXX_FLAGS and CMAKE_C_FLAGS so that
# 'config-ix' use them during feature checks. It also adds them to both
# 'LIBCXX_COMPILE_FLAGS' and 'LIBCXX_LINK_FLAGS'

if (${CMAKE_SYSTEM_NAME} MATCHES "AIX")
  add_flags_if_supported("-mdefault-visibility-export-mapping=explicit")
  set(CMAKE_AIX_EXPORT_ALL_SYMBOLS OFF)
endif()

# Configure compiler.
include(config-ix)

#===============================================================================
# Setup Compiler Flags
#===============================================================================

include(HandleLibC) # Setup the C library flags
include(HandleLibCXXABI) # Setup the ABI library flags

# FIXME(EricWF): See the FIXME on LIBCXX_ENABLE_PEDANTIC.
# Remove the -pedantic flag and -Wno-pedantic and -pedantic-errors
# so they don't get transformed into -Wno and -errors respectively.
remove_flags(-Wno-pedantic -pedantic-errors -pedantic)

# Required flags ==============================================================
function(cxx_add_basic_build_flags target)

  # Use C++23 for all targets.
  set_target_properties(${target} PROPERTIES
    CXX_STANDARD 23
    CXX_STANDARD_REQUIRED OFF # TODO: Make this REQUIRED once we don't need to accommodate the LLVM documentation builders using an ancient CMake
    CXX_EXTENSIONS NO)

  # When building the dylib, don't warn for unavailable aligned allocation
  # functions based on the deployment target -- they are always available
  # because they are provided by the dylib itself with the exception of z/OS.
  if (ZOS)
    target_add_compile_flags_if_supported(${target} PRIVATE -fno-aligned-allocation)
  else()
    target_add_compile_flags_if_supported(${target} PRIVATE -faligned-allocation)
  endif()

  # On all systems the system c++ standard library headers need to be excluded.
  # MSVC only has -X, which disables all default includes; including the crt.
  # Thus, we do nothing and hope we don't accidentally include any of the C++
  # headers
  target_add_compile_flags_if_supported(${target} PUBLIC -nostdinc++)

  # Hide all inline function definitions which have not explicitly been marked
  # visible. This prevents new definitions for inline functions from appearing in
  # the dylib when get ODR used by another function.
  target_add_compile_flags_if_supported(${target} PRIVATE -fvisibility-inlines-hidden)

  target_add_compile_flags_if_supported(${target} PRIVATE -fvisibility=hidden)

  # Build with -fsized-deallocation, which is default in recent versions of Clang.
  # TODO(LLVM 21): This can be dropped once we only support Clang >= 19.
  target_add_compile_flags_if_supported(${target} PRIVATE -fsized-deallocation)

  # Let the library headers know they are currently being used to build the
  # library.
  target_compile_definitions(${target} PRIVATE -D_LIBCPP_BUILDING_LIBRARY)

  # Make sure the library can be build without transitive includes. This makes
  # it easier to upgrade the library to a newer language standard without build
  # errors.
  target_compile_definitions(${target} PRIVATE -D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES)

  if (C_SUPPORTS_COMMENT_LIB_PRAGMA)
    if (LIBCXX_HAS_PTHREAD_LIB)
      target_compile_definitions(${target} PRIVATE -D_LIBCPP_LINK_PTHREAD_LIB)
    endif()
    if (LIBCXX_HAS_RT_LIB)
      target_compile_definitions(${target} PRIVATE -D_LIBCPP_LINK_RT_LIB)
    endif()
  endif()
  target_compile_options(${target} PUBLIC "${LIBCXX_ADDITIONAL_COMPILE_FLAGS}")
endfunction()

# Exception flags =============================================================
function(cxx_add_exception_flags target)
  if (LIBCXX_ENABLE_EXCEPTIONS)
    # Catches C++ exceptions only and tells the compiler to assume that extern C
    # functions never throw a C++ exception.
    target_add_compile_flags_if_supported(${target} PUBLIC -EHsc)
  else()
    target_add_compile_flags_if_supported(${target} PUBLIC -EHs- -EHa-)
    target_add_compile_flags_if_supported(${target} PUBLIC -fno-exceptions)
  endif()
endfunction()

# RTTI flags ==================================================================
function(cxx_add_rtti_flags target)
  if (NOT LIBCXX_ENABLE_RTTI)
    if (MSVC)
      target_add_compile_flags_if_supported(${target} PUBLIC -GR-)
    else()
      target_add_compile_flags_if_supported(${target} PUBLIC -fno-rtti)
    endif()
  endif()
endfunction()

# Modules flags ===============================================================
# FIXME The libc++ sources are fundamentally non-modular. They need special
# versions of the headers in order to provide C++03 and legacy ABI definitions.
# NOTE: The public headers can be used with modules in all other contexts.
function(cxx_add_module_flags target)
  if (LLVM_ENABLE_MODULES)
    # Ignore that the rest of the modules flags are now unused.
    target_add_compile_flags_if_supported(${target} PUBLIC -Wno-unused-command-line-argument)
    target_compile_options(${target} PUBLIC -fno-modules)
  endif()
endfunction()

string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)

# Sanitizer flags =============================================================

function(get_sanitizer_flags OUT_VAR  USE_SANITIZER)
  set(SANITIZER_FLAGS)
  set(USE_SANITIZER "${USE_SANITIZER}")
  # NOTE: LLVM_USE_SANITIZER checks for a UNIX like system instead of MSVC.
  # But we don't have LLVM_ON_UNIX so checking for MSVC is the best we can do.
  if (USE_SANITIZER AND NOT MSVC)
    append_flags_if_supported(SANITIZER_FLAGS "-fno-omit-frame-pointer")
    append_flags_if_supported(SANITIZER_FLAGS "-gline-tables-only")

    if (NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" AND
            NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "RELWITHDEBINFO")
      append_flags_if_supported(SANITIZER_FLAGS "-gline-tables-only")
    endif()
    if (USE_SANITIZER STREQUAL "Address")
      append_flags(SANITIZER_FLAGS "-fsanitize=address")
    elseif (USE_SANITIZER STREQUAL "HWAddress")
      append_flags(SANITIZER_FLAGS "-fsanitize=hwaddress")
    elseif (USE_SANITIZER MATCHES "Memory(WithOrigins)?")
      append_flags(SANITIZER_FLAGS -fsanitize=memory)
      if (USE_SANITIZER STREQUAL "MemoryWithOrigins")
        append_flags(SANITIZER_FLAGS "-fsanitize-memory-track-origins")
      endif()
    elseif (USE_SANITIZER STREQUAL "Undefined")
      append_flags(SANITIZER_FLAGS "-fsanitize=undefined" "-fno-sanitize=vptr,function" "-fno-sanitize-recover=all")
    elseif (USE_SANITIZER STREQUAL "Address;Undefined" OR
            USE_SANITIZER STREQUAL "Undefined;Address")
      append_flags(SANITIZER_FLAGS "-fsanitize=address,undefined" "-fno-sanitize=vptr,function" "-fno-sanitize-recover=all")
    elseif (USE_SANITIZER STREQUAL "Thread")
      append_flags(SANITIZER_FLAGS -fsanitize=thread)
    elseif (USE_SANITIZER STREQUAL "DataFlow")
      append_flags(SANITIZER_FLAGS -fsanitize=dataflow)
    else()
      message(WARNING "Unsupported value of LLVM_USE_SANITIZER: ${USE_SANITIZER}")
    endif()
  elseif(USE_SANITIZER AND MSVC)
    message(WARNING "LLVM_USE_SANITIZER is not supported on this platform.")
  endif()
  set(${OUT_VAR} "${SANITIZER_FLAGS}" PARENT_SCOPE)
endfunction()

get_sanitizer_flags(SANITIZER_FLAGS "${LLVM_USE_SANITIZER}")
add_library(cxx-sanitizer-flags INTERFACE)
target_compile_options(cxx-sanitizer-flags INTERFACE ${SANITIZER_FLAGS})

# _LIBCPP_INSTRUMENTED_WITH_ASAN informs that library was built with ASan.
# Defining _LIBCPP_INSTRUMENTED_WITH_ASAN while building the library with ASan is required.
# Normally, the _LIBCPP_INSTRUMENTED_WITH_ASAN flag is used to keep information whether
# dylibs are built with AddressSanitizer. However, when building libc++,
# this flag needs to be defined so that the resulting dylib has all ASan functionalities guarded by this flag.
# If the _LIBCPP_INSTRUMENTED_WITH_ASAN flag is not defined, then parts of the ASan instrumentation code in libc++
# will not be compiled into it, resulting in false positives.
# For context, read: https://github.com/llvm/llvm-project/pull/72677#pullrequestreview-1765402800
string(FIND "${LLVM_USE_SANITIZER}" "Address" building_with_asan)
if (NOT "${building_with_asan}" STREQUAL "-1")
  config_define(ON _LIBCPP_INSTRUMENTED_WITH_ASAN)
else()
  config_define(OFF _LIBCPP_INSTRUMENTED_WITH_ASAN)
endif()

# Link system libraries =======================================================
function(cxx_link_system_libraries target)
  if (NOT MSVC)
    target_link_libraries(${target} PRIVATE "-nostdlib++")
  endif()

  if (CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG AND LIBCXXABI_USE_LLVM_UNWINDER)
    # If we're linking directly against the libunwind that we're building
    # in the same invocation, don't try to link in the toolchain's
    # default libunwind (which may be missing still).
    target_add_link_flags_if_supported(${target} PRIVATE "--unwindlib=none")
  endif()

  if (MSVC)
    if (LIBCXX_USE_COMPILER_RT)
      find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY)
      if (LIBCXX_BUILTINS_LIBRARY)
        target_link_libraries(${target} PRIVATE "${LIBCXX_BUILTINS_LIBRARY}")
      endif()
    elseif (LIBCXX_HAS_GCC_LIB)
      target_link_libraries(${target} PRIVATE gcc)
    elseif (LIBCXX_HAS_GCC_S_LIB)
      target_link_libraries(${target} PRIVATE gcc_s)
    endif()
  endif()

  if (LIBCXX_HAS_ATOMIC_LIB)
    target_link_libraries(${target} PRIVATE atomic)
  endif()

  if (MINGW)
    target_link_libraries(${target} PRIVATE "${MINGW_LIBRARIES}")
  endif()

  if (MSVC)
    if ((NOT CMAKE_MSVC_RUNTIME_LIBRARY AND uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
        OR (CMAKE_MSVC_RUNTIME_LIBRARY MATCHES "Debug"))
      set(LIB_SUFFIX "d")
    else()
      set(LIB_SUFFIX "")
    endif()

    if (NOT CMAKE_MSVC_RUNTIME_LIBRARY OR CMAKE_MSVC_RUNTIME_LIBRARY MATCHES "DLL$")
      set(CRT_LIB "msvcrt")
      set(CXX_LIB "msvcprt")
    else()
      set(CRT_LIB "libcmt")
      set(CXX_LIB "libcpmt")
    endif()

    target_link_libraries(${target} PRIVATE ${CRT_LIB}${LIB_SUFFIX}) # C runtime startup files
    target_link_libraries(${target} PRIVATE ${CXX_LIB}${LIB_SUFFIX}) # C++ standard library. Required for exception_ptr internals.
    # Required for standards-complaint wide character formatting functions
    # (e.g. `printfw`/`scanfw`)
    target_link_libraries(${target} PRIVATE iso_stdio_wide_specifiers)
  endif()

  if (ANDROID AND ANDROID_PLATFORM_LEVEL LESS 21)
    target_link_libraries(${target} PUBLIC android_support)
  endif()
  target_link_libraries(${target} PUBLIC "${LIBCXX_ADDITIONAL_LIBRARIES}")
endfunction()

# Windows-related flags =======================================================
function(cxx_add_windows_flags target)
  if(WIN32 AND NOT MINGW)
    target_compile_definitions(${target} PRIVATE
                                 # Ignore the -MSC_VER mismatch, as we may build
                                 # with a different compatibility version.
                                 _ALLOW_MSC_VER_MISMATCH
                                 # Don't check the msvcprt iterator debug levels
                                 # as we will define the iterator types; libc++
                                 # uses a different macro to identify the debug
                                 # level.
                                 _ALLOW_ITERATOR_DEBUG_LEVEL_MISMATCH
                                 # We are building the c++ runtime, don't pull in
                                 # msvcprt.
                                 _CRTBLD
                                 # Don't warn on the use of "deprecated"
                                 # "insecure" functions which are standards
                                 # specified.
                                 _CRT_SECURE_NO_WARNINGS
                                 # Use the ISO conforming behaviour for conversion
                                 # in printf, scanf.
                                 _CRT_STDIO_ISO_WIDE_SPECIFIERS)
  endif()
endfunction()

# Configuration file flags =====================================================
config_define(${LIBCXX_ABI_VERSION} _LIBCPP_ABI_VERSION)
config_define(${LIBCXX_ABI_NAMESPACE} _LIBCPP_ABI_NAMESPACE)
config_define(${LIBCXX_ABI_FORCE_ITANIUM} _LIBCPP_ABI_FORCE_ITANIUM)
config_define(${LIBCXX_ABI_FORCE_MICROSOFT} _LIBCPP_ABI_FORCE_MICROSOFT)
config_define(${LIBCXX_ENABLE_THREADS} _LIBCPP_HAS_THREADS)
config_define(${LIBCXX_ENABLE_MONOTONIC_CLOCK} _LIBCPP_HAS_MONOTONIC_CLOCK)
config_define(${LIBCXX_HAS_TERMINAL_AVAILABLE} _LIBCPP_HAS_TERMINAL)
if (NOT LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION STREQUAL "default")
  config_define("${LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION}" _LIBCPP_TYPEINFO_COMPARISON_IMPLEMENTATION)
endif()
config_define(${LIBCXX_HAS_PTHREAD_API} _LIBCPP_HAS_THREAD_API_PTHREAD)
config_define(${LIBCXX_HAS_EXTERNAL_THREAD_API} _LIBCPP_HAS_THREAD_API_EXTERNAL)
config_define(${LIBCXX_HAS_WIN32_THREAD_API} _LIBCPP_HAS_THREAD_API_WIN32)
config_define(${LIBCXX_HAS_MUSL_LIBC} _LIBCPP_HAS_MUSL_LIBC)
config_define_if(LIBCXX_NO_VCRUNTIME _LIBCPP_NO_VCRUNTIME)
config_define(${LIBCXX_ENABLE_FILESYSTEM} _LIBCPP_HAS_FILESYSTEM)
config_define(${LIBCXX_ENABLE_RANDOM_DEVICE} _LIBCPP_HAS_RANDOM_DEVICE)
config_define(${LIBCXX_ENABLE_LOCALIZATION} _LIBCPP_HAS_LOCALIZATION)
config_define(${LIBCXX_ENABLE_UNICODE} _LIBCPP_HAS_UNICODE)
config_define(${LIBCXX_ENABLE_WIDE_CHARACTERS} _LIBCPP_HAS_WIDE_CHARACTERS)
config_define(${LIBCXX_ENABLE_TIME_ZONE_DATABASE} _LIBCPP_HAS_TIME_ZONE_DATABASE)
config_define(${LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS} _LIBCPP_HAS_VENDOR_AVAILABILITY_ANNOTATIONS)

# TODO: Remove in LLVM 21. We're leaving an error to make this fail explicitly.
if (LIBCXX_ENABLE_ASSERTIONS)
  message(FATAL_ERROR "LIBCXX_ENABLE_ASSERTIONS has been removed. Please use LIBCXX_HARDENING_MODE instead.")
endif()
if (LIBCXX_HARDENING_MODE STREQUAL "none")
  config_define(2 _LIBCPP_HARDENING_MODE_DEFAULT)
elseif (LIBCXX_HARDENING_MODE STREQUAL "fast")
  config_define(4 _LIBCPP_HARDENING_MODE_DEFAULT)
elseif (LIBCXX_HARDENING_MODE STREQUAL "extensive")
  config_define(16 _LIBCPP_HARDENING_MODE_DEFAULT)
elseif (LIBCXX_HARDENING_MODE STREQUAL "debug")
  config_define(8 _LIBCPP_HARDENING_MODE_DEFAULT)
endif()

if (LIBCXX_PSTL_BACKEND STREQUAL "serial")
  config_define(1 _LIBCPP_PSTL_BACKEND_SERIAL)
elseif(LIBCXX_PSTL_BACKEND STREQUAL "std_thread")
  config_define(1 _LIBCPP_PSTL_BACKEND_STD_THREAD)
elseif(LIBCXX_PSTL_BACKEND STREQUAL "libdispatch")
  config_define(1 _LIBCPP_PSTL_BACKEND_LIBDISPATCH)
else()
  message(FATAL_ERROR "LIBCXX_PSTL_BACKEND is set to ${LIBCXX_PSTL_BACKEND}, which is not a valid backend.
                       Valid backends are: serial, std_thread and libdispatch")
endif()

if (LIBCXX_ABI_DEFINES)
  set(abi_defines)
  foreach (abi_define ${LIBCXX_ABI_DEFINES})
    if (NOT abi_define MATCHES "^_LIBCPP_ABI_")
      message(SEND_ERROR "Invalid ABI macro ${abi_define} in LIBCXX_ABI_DEFINES")
    endif()
    list(APPEND abi_defines "#define ${abi_define}")
  endforeach()
  string(REPLACE ";" "\n" abi_defines "${abi_defines}")
  config_define(${abi_defines} _LIBCPP_ABI_DEFINES)
endif()

if (LIBCXX_EXTRA_SITE_DEFINES)
  set(extra_site_defines)
  foreach (extra_site_define ${LIBCXX_EXTRA_SITE_DEFINES})
    # Allow defines such as DEFINE=VAL, transformed into "#define DEFINE VAL".
    string(REPLACE "=" " " extra_site_define "${extra_site_define}")
    list(APPEND extra_site_defines "#define ${extra_site_define}")
  endforeach()
  string(REPLACE ";" "\n" extra_site_defines "${extra_site_defines}")
  config_define(${extra_site_defines} _LIBCPP_EXTRA_SITE_DEFINES)
endif()

# By default libc++ on Windows expects to use a shared library, which requires
# the headers to use DLL import/export semantics. However when building a
# static library only we modify the headers to disable DLL import/export.
if (DEFINED WIN32 AND LIBCXX_ENABLE_STATIC AND NOT LIBCXX_ENABLE_SHARED)
  message(STATUS "Generating custom __config for non-DLL Windows build")
  config_define(ON _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
endif()

if (WIN32 AND LIBCXX_ENABLE_STATIC_ABI_LIBRARY)
  # If linking libcxxabi statically into libcxx, skip the dllimport attributes
  # on symbols we refer to from libcxxabi.
  add_definitions(-D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS)
endif()

# Setup all common build flags =================================================
function(cxx_add_common_build_flags target)
  cxx_add_basic_build_flags(${target})
  cxx_add_warning_flags(${target} ${LIBCXX_ENABLE_WERROR} ${LIBCXX_ENABLE_PEDANTIC})
  cxx_add_windows_flags(${target})
  cxx_add_exception_flags(${target})
  cxx_add_rtti_flags(${target})
  cxx_add_module_flags(${target})
  cxx_link_system_libraries(${target})
  target_link_libraries(${target} PRIVATE cxx-sanitizer-flags)
endfunction()

#===============================================================================
# Setup Source Code And Tests
#===============================================================================
add_custom_target(cxx-test-depends
  COMMENT "Build dependencies required to run the libc++ test suite.")

add_subdirectory(include)
add_subdirectory(src)
add_subdirectory(utils)
add_subdirectory(modules)

if (LIBCXX_INCLUDE_TESTS)
  add_subdirectory(test)
  add_subdirectory(lib/abi)
endif()

if (LIBCXX_INCLUDE_DOCS)
  add_subdirectory(docs)
endif()