[libcxx][CMake] Add install path variable to allow overriding the destination

[phosek]

Summary

This is going to be used by the runtime build in the multi-target setup to allow using different install prefix for each target.

[EricWF]

Please add an entry for this option in the BuildingLibcxx.rst file, under the CMake options heading.

[EricWF]

Oh, shoot nevermind abouth the LGTM. This needs changes to the testsuite as well, since it needs to be taught where to find libc++.

Also isn't there a CMake PREFIX variable we can set to change this globally?

[phosek]

There's CMAKE_PREFIX_PATH, the problem is that this is a global setting which works fine when building libc++ as standalone or as part of LLVM only for a single target. However, with D32816 we would like to add a support for building runtimes for multiple targets and hence we need a way to customize the install path for individual targets.

[phosek]

I have updated the documentation. I've checked the test suite but I don't think there's anything that needs to change there as this option is only used during installation.

[jroelofs]

@EricWF we don't do any installed testing, only testing from the build dir, right?

[phosek]

@beanz does this make sense?

[beanz]

This LGTM.

CMakeLists.txt

 set(LIBCXX_BINARY_INCLUDE_DIR "${LIBCXX_BINARY_DIR}/include/c++build")
 if (LLVM_LIBRARY_OUTPUT_INTDIR)
   set(LIBCXX_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
 else()
   set(LIBCXX_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LIBCXX_LIBDIR_SUFFIX})
 endif()
 file(MAKE_DIRECTORY "${LIBCXX_BINARY_INCLUDE_DIR}")
 
+set(LIBCXX_INSTALL_PREFIX "" CACHE PATH
+    "Define libc++ destination prefix.")
+
 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.

cmake/Modules/HandleLibCXXABI.cmake

foreach(incpath ${LIBCXX_CXX_ABI_INCLUDE_PATHS})
         file(COPY "${incpath}/${fpath}"
           DESTINATION "${LIBCXX_BINARY_INCLUDE_DIR}/${dstdir}"
           )
         file(COPY "${incpath}/${fpath}"
           DESTINATION "${CMAKE_BINARY_DIR}/include/c++/v1/${dstdir}"
           )
         if (LIBCXX_INSTALL_HEADERS)
           install(FILES "${LIBCXX_BINARY_INCLUDE_DIR}/${fpath}"
-            DESTINATION include/c++/v1/${dstdir}
+            DESTINATION ${LIBCXX_INSTALL_PREFIX}include/c++/v1/${dstdir}
             COMPONENT libcxx
             PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
             )
         endif()
         list(APPEND abilib_headers "${LIBCXX_BINARY_INCLUDE_DIR}/${fpath}")
       endif()
     endforeach()
     if (NOT found)

docs/BuildingLibcxx.rst

.. option:: LIBCXX_ENABLE_STATIC:BOOL
   Build libc++ as a static library. Either `LIBCXX_ENABLE_SHARED` or
   `LIBCXX_ENABLE_STATIC` has to be enabled.
 
 .. option:: LIBCXX_LIBDIR_SUFFIX:STRING
 
   Extra suffix to append to the directory where libraries are to be installed.
   This option overrides `LLVM_LIBDIR_SUFFIX`.
 
+.. option:: LIBCXX_INSTALL_PATH:STRING
+
+  **Default**: ``CMAKE_INSTALL_PREFIX``
+
+  Path where libc++ library should be installed.
 
 .. _libc++experimental options:
 
 libc++experimental Specific Options
 ------------------------------------
 
 .. option:: LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY:BOOL
 

include/CMakeLists.txt

file(COPY .
     DESTINATION "${LLVM_BINARY_DIR}/include/c++/v1"
     FILES_MATCHING
     ${LIBCXX_HEADER_PATTERN}
     )
 endif()
 
 if (LIBCXX_INSTALL_HEADERS)
   install(DIRECTORY .
-    DESTINATION include/c++/v1
+    DESTINATION ${LIBCXX_INSTALL_PREFIX}include/c++/v1
     COMPONENT cxx-headers
     FILES_MATCHING
     ${LIBCXX_HEADER_PATTERN}
     PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
   )
 
   if (LIBCXX_NEEDS_SITE_CONFIG)
     # Generate and install 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
       DEPENDS ${LIBCXX_BINARY_DIR}/__generated_config)
     set(generated_config_deps generate_config_header)
     # Install the generated header as __config.
     install(FILES ${LIBCXX_BINARY_DIR}/__generated_config
-      DESTINATION include/c++/v1
+      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)

lib/CMakeLists.txt

if (LIBCXX_ENABLE_SHARED AND LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
   )
 endif()
 
 if (LIBCXX_INSTALL_LIBRARY)
   if (LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY)
     set(experimental_lib cxx_experimental)
   endif()
   install(TARGETS ${LIBCXX_TARGETS} ${experimental_lib}
-    LIBRARY DESTINATION lib${LIBCXX_LIBDIR_SUFFIX} COMPONENT cxx
-    ARCHIVE DESTINATION lib${LIBCXX_LIBDIR_SUFFIX} COMPONENT cxx
+    LIBRARY DESTINATION ${LIBCXX_INSTALL_PREFIX}lib${LIBCXX_LIBDIR_SUFFIX} COMPONENT cxx
+    ARCHIVE DESTINATION ${LIBCXX_INSTALL_PREFIX}lib${LIBCXX_LIBDIR_SUFFIX} COMPONENT cxx
     )
   # NOTE: This install command must go after the cxx install command otherwise
   # it will not be executed after the library symlinks are installed.
   if (LIBCXX_ENABLE_SHARED AND LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
     # Replace the libc++ filename with $<TARGET_LINKER_FILE:cxx>
     # after we required CMake 3.0.
     install(FILES "${LIBCXX_LIBRARY_DIR}/libc++${CMAKE_SHARED_LIBRARY_SUFFIX}"
-      DESTINATION lib${LIBCXX_LIBDIR_SUFFIX}
+      DESTINATION ${LIBCXX_INSTALL_PREFIX}lib${LIBCXX_LIBDIR_SUFFIX}
       COMPONENT libcxx)
   endif()
 endif()
 
 if (NOT CMAKE_CONFIGURATION_TYPES AND (LIBCXX_INSTALL_LIBRARY OR
                                        LIBCXX_INSTALL_HEADERS))
     if(LIBCXX_INSTALL_LIBRARY)
       set(lib_install_target cxx)