[CMake] Use custom command and target to install libc++ headers

[phosek]

Summary

Using file(COPY FILE...) has several downsides. Since the file command
is only executed at configuration time, any changes to headers made
after the initial CMake execution are ignored. This can lead to subtle
errors since the just built Clang will be using stale libc++ headers.
Furthermore, since the headers are copied prior to executing the build
system, this may hide missing dependencies on libc++ from other LLVM
components.

This changes replaces the use of file(COPY FILE...) command with a
custom command and target which addresses all aforementioned issues and
matches the implementation already used by other LLVM components that
also install headers like Clang builtin headers.

[phosek]

This changes has already revealed some missing libc++ dependencies in sanitizers which were masked by the use of file(COPY FILE...).

[phosek]

ping

[EricWF]

This LGTM modulo requested changes.

There's a section in NOTES.TXT about the steps required for adding a header. Please update that to mention listing it in CMake.

libcxx/include/CMakeLists.txt

151

We still want to install the experimental headers even if the experimental library build isn't enabled. Header only components still function.

[EricWF]

There are a couple of new headers, <version> and <compare> that should be added to the list before committing.

libcxx/NOTES.TXT

 //===---------------------------------------------------------------------===//
 
 These notes contain a list of things that must be done upon adding a new header
 to libc++.
 
 1. Add a test under `test/libcxx` that the header defines `_LIBCPP_VERSION`.
 2. Update `test/libcxx/double_include.sh.cpp` to include the new header.
 3. Create a submodule in `include/module.modulemap` for the new header.
+4. Update the include/CMakeLists.txt file to include the new header.

libcxx/cmake/Modules/HandleLibCXXABI.cmake

macro(setup_abi_lib abidefines abilib abifiles abidirs)
 
   foreach(fpath ${LIBCXX_ABILIB_FILES})
     set(found FALSE)
     foreach(incpath ${LIBCXX_CXX_ABI_INCLUDE_PATHS})
       if (EXISTS "${incpath}/${fpath}")
         set(found TRUE)
         get_filename_component(dstdir ${fpath} PATH)
         get_filename_component(ifile ${fpath} NAME)
-        file(COPY "${incpath}/${fpath}"
-          DESTINATION "${LIBCXX_BINARY_INCLUDE_DIR}/${dstdir}"
-          )
-        file(COPY "${incpath}/${fpath}"
-          DESTINATION "${CMAKE_BINARY_DIR}/include/c++/v1/${dstdir}"
-          )
+        set(src ${incpath}/${fpath})
+
+        set(dst ${LIBCXX_BINARY_INCLUDE_DIR}/${dstdir}/${fpath})
+        add_custom_command(OUTPUT ${dst}
+            DEPENDS ${src}
+            COMMAND ${CMAKE_COMMAND} -E copy_if_different ${src} ${dst}
+            COMMENT "Copying C++ ABI header ${fpath}...")
+        list(APPEND abilib_headers "${dst}")
+
+        set(dst "${CMAKE_BINARY_DIR}/include/c++/v1/${dstdir}/${fpath}")
+        add_custom_command(OUTPUT ${dst}
+            DEPENDS ${src}
+            COMMAND ${CMAKE_COMMAND} -E copy_if_different ${src} ${dst}
+            COMMENT "Copying C++ ABI header ${fpath}...")
+        list(APPEND abilib_headers "${dst}")
+
         if (LIBCXX_INSTALL_HEADERS)
           install(FILES "${LIBCXX_BINARY_INCLUDE_DIR}/${fpath}"
             DESTINATION ${LIBCXX_INSTALL_PREFIX}include/c++/v1/${dstdir}
             COMPONENT cxx-headers
             PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
             )
         endif()
-        list(APPEND abilib_headers "${LIBCXX_BINARY_INCLUDE_DIR}/${fpath}")
       endif()
     endforeach()
     if (NOT found)
       message(WARNING "Failed to find ${fpath}")
     endif()
   endforeach()
 
   include_directories("${LIBCXX_BINARY_INCLUDE_DIR}")
+  add_custom_target(cxx-abi-headers ALL DEPENDS ${abilib_headers})
 endmacro()
 
 
 # Configure based on the selected ABI library.
 if ("${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "libstdc++" OR
     "${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "libsupc++")
   set(_LIBSUPCXX_INCLUDE_FILES
     cxxabi.h bits/c++config.h bits/os_defines.h bits/cpu_defines.h

libcxx/include/CMakeLists.txt

-if (NOT LIBCXX_INSTALL_SUPPORT_HEADERS)
-  set(LIBCXX_SUPPORT_HEADER_PATTERN PATTERN "support" EXCLUDE)
+set(files
+  __bit_reference
+  __bsd_locale_defaults.h
+  __bsd_locale_fallbacks.h
+  __debug
+  __functional_03
+  __functional_base
+  __functional_base_03
+  __hash_table
+  __libcpp_version
+  __locale
+  __mutex_base
+  __nullptr
+  __split_buffer
+  __sso_allocator
+  __std_stream
+  __string
+  __threading_support
+  __tree
+  __tuple
+  __undef_macros
+  algorithm
+  any
+  array
+  atomic
+  bitset
+  cassert
+  ccomplex
+  cctype
+  cerrno
+  cfenv
+  cfloat
+  chrono
+  cinttypes
+  ciso646
+  climits
+  clocale
+  cmath
+  codecvt
+  complex
+  complex.h
+  condition_variable
+  csetjmp
+  csignal
+  cstdarg
+  cstdbool
+  cstddef
+  cstdint
+  cstdio
+  cstdlib
+  cstring
+  ctgmath
+  ctime
+  ctype.h
+  cwchar
+  cwctype
+  deque
+  errno.h
+  exception
+  experimental/__config
+  experimental/__memory
+  experimental/algorithm
+  experimental/any
+  experimental/chrono
+  experimental/coroutine
+  experimental/deque
+  experimental/dynarray
+  experimental/filesystem
+  experimental/forward_list
+  experimental/functional
+  experimental/iterator
+  experimental/list
+  experimental/map
+  experimental/memory_resource
+  experimental/numeric
+  experimental/optional
+  experimental/propagate_const
+  experimental/ratio
+  experimental/regex
+  experimental/set
+  experimental/string
+  experimental/string_view
+  experimental/system_error
+  experimental/tuple
+  experimental/type_traits
+  experimental/unordered_map
+  experimental/unordered_set
+  experimental/utility
+  experimental/vector
+  ext/__hash
+  ext/hash_map
+  ext/hash_set
+  float.h
+  forward_list
+  fstream
+  functional
+  future
+  initializer_list
+  inttypes.h
+  iomanip
+  ios
+  iosfwd
+  iostream
+  istream
+  iterator
+  limits
+  limits.h
+  list
+  locale
+  locale.h
+  map
+  math.h
+  memory
+  module.modulemap
+  mutex
+  new
+  numeric
+  optional
+  ostream
+  queue
+  random
+  ratio
+  regex
+  scoped_allocator
+  set
+  setjmp.h
+  shared_mutex
+  sstream
+  stack
+  stdbool.h
+  stddef.h
+  stdexcept
+  stdint.h
+  stdio.h
+  stdlib.h
+  streambuf
+  string
+  string.h
+  string_view
+  strstream
+  system_error
+  tgmath.h
+  thread
+  tuple
+  type_traits
+  typeindex
+  typeinfo
+  unordered_map
+  unordered_set
+  utility
+  valarray
+  variant
+  vector
+  wchar.h
+  wctype.h
+  )
+
+if(LIBCXX_INSTALL_SUPPORT_HEADERS)
+  set(files
+    ${files}
+    support/android/locale_bionic.h
+    support/fuchsia/xlocale.h
+    support/ibm/limits.h
+    support/ibm/locale_mgmt_aix.h
+    support/ibm/support.h
+    support/ibm/xlocale.h
+    support/musl/xlocale.h
+    support/newlib/xlocale.h
+    support/solaris/floatingpoint.h
+    support/solaris/wchar.h
+    support/solaris/xlocale.h
+    support/win32/limits_msvc_win32.h
+    support/win32/locale_win32.h
+    support/xlocale/__nop_locale_mgmt.h
+    support/xlocale/__posix_l_fallback.h
+    support/xlocale/__strtonum_fallback.h
+    support/xlocale/xlocale.h
+    )
 endif()
 
 if (LIBCXX_NEEDS_SITE_CONFIG)
   # Generate a custom __config header. The new header is created
   # by prepending __config_site to the current __config header.
   add_custom_command(OUTPUT ${LIBCXX_BINARY_DIR}/__generated_config
     COMMAND ${PYTHON_EXECUTABLE} ${LIBCXX_SOURCE_DIR}/utils/cat_files.py
       ${LIBCXX_BINARY_DIR}/__config_site
       ${LIBCXX_SOURCE_DIR}/include/__config
       -o ${LIBCXX_BINARY_DIR}/__generated_config
     DEPENDS ${LIBCXX_SOURCE_DIR}/include/__config
             ${LIBCXX_BINARY_DIR}/__config_site
   )
   # Add a target that executes the generation commands.
-  add_custom_target(generate_config_header ALL
+  add_custom_target(cxx-generated-config ALL
     DEPENDS ${LIBCXX_BINARY_DIR}/__generated_config)
-  set(generated_config_deps generate_config_header)
-endif()
-
-set(LIBCXX_HEADER_PATTERN
-  PATTERN "*"
-  PATTERN "CMakeLists.txt" EXCLUDE
-  PATTERN ".svn" EXCLUDE
-  PATTERN "__config_site.in" EXCLUDE
-  ${LIBCXX_SUPPORT_HEADER_PATTERN}
+  set(generated_config_deps cxx-generated-config)
+else()
+  set(files
+    ${files}
+    __config
     )
+endif()
 
 if(NOT LIBCXX_USING_INSTALLED_LLVM AND LLVM_BINARY_DIR)
-  file(COPY .
-    DESTINATION "${LLVM_BINARY_DIR}/include/c++/v1"
-    FILES_MATCHING
-    ${LIBCXX_HEADER_PATTERN}
-    )
+  set(output_dir ${LLVM_BINARY_DIR}/include/c++/v1)
+
+  set(out_files)
+  foreach(f ${files})
+    set(src ${CMAKE_CURRENT_SOURCE_DIR}/${f})
+    set(dst ${output_dir}/${f})
+    add_custom_command(OUTPUT ${dst}
+      DEPENDS ${src}
+      COMMAND ${CMAKE_COMMAND} -E copy_if_different ${src} ${dst}
+      COMMENT "Copying libc++'s ${f}...")
+    list(APPEND out_files ${dst})
+  endforeach()
 
   if (LIBCXX_NEEDS_SITE_CONFIG)
     # Copy the generated header as __config into build directory.
-    add_custom_command(
-        TARGET generate_config_header POST_BUILD
-        COMMAND ${CMAKE_COMMAND} -E copy
-                ${LIBCXX_BINARY_DIR}/__generated_config
-                ${LLVM_BINARY_DIR}/include/c++/v1/__config)
+    set(src ${LIBCXX_BINARY_DIR}/__generated_config)
+    set(dst ${output_dir}/__config)
+    add_custom_command(OUTPUT ${dst}
+        DEPENDS ${src} ${generated_config_deps}
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different ${src} ${dst}
+        COMMENT "Copying libc++'s __config")
+    list(APPEND out_files ${dst})
   endif()
+
+  add_custom_target(cxx-headers ALL DEPENDS ${out_files} ${abilib_headers})
+else()
+  add_custom_target(cxx-headers)
 endif()
+set_target_properties(cxx-headers PROPERTIES FOLDER "Misc")
 
 if (LIBCXX_INSTALL_HEADERS)
-  install(DIRECTORY .
-    DESTINATION ${LIBCXX_INSTALL_PREFIX}include/c++/v1
+  foreach(file ${files})
+    get_filename_component(dir ${file} DIRECTORY)
+    install(FILES ${file}
+      DESTINATION ${LIBCXX_INSTALL_PREFIX}include/c++/v1/${dir}
       COMPONENT cxx-headers
-    FILES_MATCHING
-    ${LIBCXX_HEADER_PATTERN}
       PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
     )
+  endforeach()
 
   if (LIBCXX_NEEDS_SITE_CONFIG)
     # Install the generated header as __config.
     install(FILES ${LIBCXX_BINARY_DIR}/__generated_config
       DESTINATION ${LIBCXX_INSTALL_PREFIX}include/c++/v1
       PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
       RENAME __config
       COMPONENT cxx-headers)
   endif()
 
   if (NOT CMAKE_CONFIGURATION_TYPES)
-    # this target is just needed as a placeholder for the distribution target
-    add_custom_target(cxx-headers)
     add_custom_target(install-cxx-headers
                       DEPENDS cxx-headers ${generated_config_deps}
                       COMMAND "${CMAKE_COMMAND}"
                               -DCMAKE_INSTALL_COMPONENT=cxx-headers
                               -P "${CMAKE_BINARY_DIR}/cmake_install.cmake")
     # Stripping is a no-op for headers
     add_custom_target(install-cxx-headers-stripped DEPENDS install-cxx-headers)
 
-    add_custom_target(libcxx-headers)
     add_custom_target(install-libcxx-headers DEPENDS install-cxx-headers)
     add_custom_target(install-libcxx-headers-stripped DEPENDS install-cxx-headers-stripped)
   endif()
 endif()

libcxx/lib/CMakeLists.txt

ARGS
       "${MERGE_ARCHIVES_ABI_TARGET}"
       "${MERGE_ARCHIVES_SEARCH_PATHS}"
     WORKING_DIRECTORY ${LIBCXX_BUILD_DIR}
     )
   endif()
 endif()
 
 # Add a meta-target for both libraries.
-add_custom_target(cxx DEPENDS ${LIBCXX_TARGETS} ${generated_config_deps})
+add_custom_target(cxx DEPENDS ${LIBCXX_TARGETS})
+add_dependencies(cxx cxx-headers)
 
 if (LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY)
   file(GLOB LIBCXX_EXPERIMENTAL_SOURCES ../src/experimental/*.cpp)
   if (LIBCXX_ENABLE_FILESYSTEM)
     file(GLOB LIBCXX_FILESYSTEM_SOURCES ../src/experimental/filesystem/*.cpp)
   endif()
   add_library(cxx_experimental STATIC ${LIBCXX_EXPERIMENTAL_SOURCES} ${LIBCXX_FILESYSTEM_SOURCES})
   if (LIBCXX_ENABLE_SHARED)