[libc++abi] Install the libc++abi headers from libc++abi

[ldionne]

Summary

libc++abi should be responsible for installing its own headers, it
doesn't make sense for libc++ to be responsible for it.

[ldionne]

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

271–281 ↗

(On Diff #341195)

Trying to save you a headache @thakis, but I'd like you to double-check this is OK.

[phosek]

LGTM

libcxx/cmake/Modules/HandleLibCXXABI.cmake

15 ↗

(On Diff #341195)

We should also consider inlining this macro, I don't think it's getting us anything and I always have to lookup what each argument does so at least in my experience it harms readability.

[thakis]

Makes sense to me.

Just to confirm: Even back when clang assumed that libc++ headers shipped with the compiler instead of the sdk on macOS (which I think is still the case in currently shipping xcode), it didn't assume that the libc++abi headers ship with the compiler, right? (I patched this in and clang still seems to compile a program that includes <iostream> fine, so it looks like it.)

Is there anything else that installs this header? We don't need it, but someone might?

[ldionne]

In D101458#2723626, @thakis wrote:

Makes sense to me.

Just to confirm: Even back when clang assumed that libc++ headers shipped with the compiler instead of the sdk on macOS (which I think is still the case in currently shipping xcode), it didn't assume that the libc++abi headers ship with the compiler, right? (I patched this in and clang still seems to compile a program that includes <iostream> fine, so it looks like it.)

Fact: Clang used to assume that libc++ was shipped in <toolchain>/include/c++/v1, and nowadays it looks in <sdk>/include/c++/v1 first, and only falls back to <toolchain>/include/c++/v1.
Fact: Recent SDKs have the libc++ headers in <sdk>/usr/include/c++/v1.
Fact: The <cxxabi.h> header is present in both <sdk>/usr/include/c++/v1 and <sdk>/usr/include (and also in <toolchain>/usr/include/c++/v1 until we remove all traces of libc++/libc++abi from the toolchain). It looks like they are always the same thing. It's harmless but silly, since we should really have only one copy. It turns out I don't understand how the copy in <sdk>/usr/include ends up there, so I'll investigate that.

Your main question: I'm pretty sure Clang used to expect <cxxabi.h> in <toolchain>/usr/include/c++/v1, alongside the rest of libc++.

I actually hadn't realized that, and it does change what I was going to do. Instead of always installing <cxxabi.h> to <install>/usr/include, I think the correct thing to do would be to always install it to <install>/usr/include/c++/v1, but to do that directly from libc++abi. My next update will reflect that.

Edit I just found out where <sdk>/usr/include/cxxabi.h comes from. We copy it explicitly here: https://github.com/llvm/llvm-project/blob/main/libcxx/utils/ci/apple-install-libcxx.sh#L159. I wrote that code, I should have known!

libcxx/cmake/Modules/HandleLibCXXABI.cmake

15 ↗

(On Diff #341195)

Oh yeah, totally, I want to clean up this mess, one step at a time.

[ldionne]

Install <cxxabi.h> from libc++abi.

Pinging @dim since I think you folks use a different ABI library - you should make
sure that your ABI library is installing <cxxabi.h> in a place where users can find
it on its own.

[ldionne]

Drop the gn changes.

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

271–281 ↗

(On Diff #341195)

@thakis I suspect you'll have more fixing up to do since you need to install the libc++abi headers from the libc++abi build. I'll just drop this GN change to avoid muddying the waters, but I'm still giving you this heads up.

[ldionne]

Link cxx_static against libc++abi to get the header dependency.

[ldionne]

Rebase onto main, and don't touch any logic inside libc++. In other words, only start installing
the headers from libc++abi. I'll keep any potentially-breaking change in a separate patch.

[ldionne]

Rebase onto main -- I am unable to reproduce the CI issue with GCC, and it looks like a fluke to me.

libcxx/utils/ci/apple-install-libcxx.sh

 fi
 
 # Install the headers by copying the headers from one of the built architectures
 # into the install directory. Headers from all architectures should be the same.
 step "Installing the libc++ and libc++abi headers to ${install_dir}/usr/include"
 any_arch=$(echo ${architectures} | cut -d ' ' -f 1)
 mkdir -p "${install_dir}/usr/include"
 ditto "${build_dir}/${any_arch}-install/include" "${install_dir}/usr/include"
-ditto "${llvm_root}/libcxxabi/include" "${install_dir}/usr/include" # TODO: libcxxabi should install its headers in CMake
 if [[ $EUID -eq 0 ]]; then # Only chown if we're running as root
     chown -R root:wheel "${install_dir}/usr/include"
 fi
 
 if [ "$headers_only" != true ]; then
     step "Installing the libc++ and libc++abi licenses"
     mkdir -p "${install_dir}/usr/local/OpenSourceLicenses"
     cp "${llvm_root}/libcxx/LICENSE.TXT" "${install_dir}/usr/local/OpenSourceLicenses/libcxx.txt"

libcxxabi/CMakeLists.txt

 option(LIBCXXABI_BUILD_32_BITS "Build 32 bit multilib libc++abi. This option is not supported anymore when building the runtimes. Please specify a full triple instead." ${LLVM_BUILD_32_BITS})
 if (LIBCXXABI_BUILD_32_BITS)
   message(FATAL_ERROR "LIBCXXABI_BUILD_32_BITS is not supported anymore when building the runtimes, please specify a full triple instead.")
 endif()
 
 option(LIBCXXABI_INCLUDE_TESTS "Generate build targets for the libc++abi unit tests." ${LLVM_INCLUDE_TESTS})
 set(LIBCXXABI_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING
     "Define suffix of library directory name (32/64)")
+option(LIBCXXABI_INSTALL_HEADERS "Install the libc++abi headers." ON)
 option(LIBCXXABI_INSTALL_LIBRARY "Install the libc++abi library." ON)
+set(LIBCXXABI_INSTALL_INCLUDE_DIR "include/c++/v1" CACHE PATH "Path to install the libc++abi headers at.")
 
 if(NOT CMAKE_SYSROOT AND LIBCXXABI_SYSROOT)
   message(WARNING "LIBCXXABI_SYSROOT is deprecated, please use CMAKE_SYSROOT instead")
 endif()
 if(NOT CMAKE_CXX_COMPILER_TARGET AND LIBCXXABI_TARGET_TRIPLE)
   message(WARNING "LIBCXXABI_TARGET_TRIPLE is deprecated, please use CMAKE_CXX_COMPILER_TARGET instead")
 endif()
 if(NOT CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN AND LIBCXXABI_GCC_TOOLCHAIN)

 # Setup Source Code
 #===============================================================================
 
 set(LIBCXXABI_LIBUNWIND_INCLUDES "${LIBCXXABI_LIBUNWIND_INCLUDES}" CACHE PATH
     "Specify path to libunwind includes." FORCE)
 set(LIBCXXABI_LIBUNWIND_PATH "${LIBCXXABI_LIBUNWIND_PATH}" CACHE PATH
     "Specify path to libunwind source." FORCE)
 
-include_directories(include)
 if (LIBCXXABI_USE_LLVM_UNWINDER OR LLVM_NATIVE_ARCH MATCHES ARM)
   find_path(LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL libunwind.h
     PATHS ${LIBCXXABI_LIBUNWIND_INCLUDES}
           ${LIBCXXABI_LIBUNWIND_PATH}/include
           ${CMAKE_BINARY_DIR}/${LIBCXXABI_LIBUNWIND_INCLUDES}
           ${LLVM_MAIN_SRC_DIR}/projects/libunwind/include
           ${LLVM_MAIN_SRC_DIR}/runtimes/libunwind/include
           ${LLVM_MAIN_SRC_DIR}/../libunwind/include
     NO_DEFAULT_PATH
     NO_CMAKE_FIND_ROOT_PATH
   )
 
   if (LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL STREQUAL "LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL-NOTFOUND")
     set(LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL "")
   endif()
 
   if (NOT LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL STREQUAL "")
     include_directories("${LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL}")
   endif()
 endif()
 
 # Add source code. This also contains all of the logic for deciding linker flags
 # soname, etc...
+add_subdirectory(include)
 add_subdirectory(src)
 
 if (LIBCXXABI_INCLUDE_TESTS)
   add_subdirectory(test)
   add_subdirectory(fuzz)
 endif()

libcxxabi/include/CMakeLists.txt

+set(files
+  __cxxabi_config.h
+  cxxabi.h
+  )
+
+add_library(cxxabi-headers INTERFACE)
+target_include_directories(cxxabi-headers INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}")
+
+if (LIBCXXABI_INSTALL_HEADERS)
+  foreach(file ${files})
+    get_filename_component(dir ${file} DIRECTORY)
+    install(FILES ${file}
+      DESTINATION ${LIBCXXABI_INSTALL_INCLUDE_DIR}/${dir}
+      COMPONENT cxxabi-headers
+      PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
+    )
+  endforeach()
+
+  add_custom_target(install-cxxabi-headers
+                    DEPENDS cxxabi-headers
+                    COMMAND "${CMAKE_COMMAND}"
+                            -DCMAKE_INSTALL_COMPONENT=cxxabi-headers
+                            -P "${CMAKE_BINARY_DIR}/cmake_install.cmake")
+  # Stripping is a no-op for headers
+  add_custom_target(install-cxxabi-headers-stripped DEPENDS install-cxxabi-headers)
+endif()

libcxxabi/src/CMakeLists.txt

 if (NOT TARGET pstl::ParallelSTL)
   message(STATUS "Could not find ParallelSTL, libc++abi will not attempt to use it but the build may fail if the libc++ in use needs it to be available.")
 endif()
 
 # Build the shared library.
 if (LIBCXXABI_ENABLE_SHARED)
   add_library(cxxabi_shared SHARED ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
   target_link_libraries(cxxabi_shared PRIVATE cxx-headers ${LIBCXXABI_SHARED_LIBRARIES} ${LIBCXXABI_LIBRARIES})
+  target_link_libraries(cxxabi_shared PUBLIC cxxabi-headers)
   if (TARGET pstl::ParallelSTL)
     target_link_libraries(cxxabi_shared PUBLIC pstl::ParallelSTL)
   endif()
   set_target_properties(cxxabi_shared
     PROPERTIES
       CXX_EXTENSIONS OFF
       CXX_STANDARD 20
       CXX_STANDARD_REQUIRED OFF
if (APPLE)
     endif()
   endif()
 endif()
 
 # Build the static library.
 if (LIBCXXABI_ENABLE_STATIC)
   add_library(cxxabi_static STATIC ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
   target_link_libraries(cxxabi_static PRIVATE cxx-headers ${LIBCXXABI_STATIC_LIBRARIES} ${LIBCXXABI_LIBRARIES})
+  target_link_libraries(cxxabi_static PUBLIC cxxabi-headers)
   if (TARGET pstl::ParallelSTL)
     target_link_libraries(cxxabi_static PUBLIC pstl::ParallelSTL)
   endif()
   set_target_properties(cxxabi_static
     PROPERTIES
       CXX_EXTENSIONS OFF
       CXX_STANDARD 20
       CXX_STANDARD_REQUIRED OFF
install(TARGETS ${LIBCXXABI_INSTALL_TARGETS}
     LIBRARY DESTINATION ${LIBCXXABI_INSTALL_LIBRARY_DIR} COMPONENT cxxabi
     ARCHIVE DESTINATION ${LIBCXXABI_INSTALL_LIBRARY_DIR} COMPONENT cxxabi
     RUNTIME DESTINATION ${LIBCXXABI_INSTALL_RUNTIME_DIR} COMPONENT cxxabi
     )
 endif()
 
 if (NOT CMAKE_CONFIGURATION_TYPES AND LIBCXXABI_INSTALL_LIBRARY)
   add_custom_target(install-cxxabi
-    DEPENDS cxxabi
+    DEPENDS cxxabi install-cxxabi-headers
     COMMAND "${CMAKE_COMMAND}"
             -DCMAKE_INSTALL_COMPONENT=cxxabi
             -P "${LIBCXXABI_BINARY_DIR}/cmake_install.cmake")
   add_custom_target(install-cxxabi-stripped
     DEPENDS cxxabi
     COMMAND "${CMAKE_COMMAND}"
             -DCMAKE_INSTALL_COMPONENT=cxxabi
             -DCMAKE_INSTALL_DO_STRIP=1
             -P "${LIBCXXABI_BINARY_DIR}/cmake_install.cmake")
 endif()