[CMake] Set the default ABI version for Fuchsia in CMake as well

[phosek]

Summary

This is neeeded since the CMake value is used for the SOVERSION.

[phosek]

ping?

[smeenai]

This LGTM given that Eric accepted your previous change. I'm happy to accept it in a day or two if he hasn't gotten the chance to take a look by then.

libcxx/CMakeLists.txt

101

I prefer DEFAULT_ABI_VERSION to ABI_VERSION_DEFAULT

[phosek]

I had something similar in D45304 but Eric suggested removing it. What I haven't realized is that this value is also used to set the SOVERSION so it's indeed needed.

[EricWF]

OK, so we need to bump the SO version -- However I don't want to generate a site_config header because of that if the config header is sufficient. I would like to see a solution that takes that into account.

[phosek]

In D45529#1066394, @EricWF wrote:

OK, so we need to bump the SO version -- However I don't want to generate a site_config header because of that if the config header is sufficient. I would like to see a solution that takes that into account.

There shouldn't be any __site_config generated now since we compare LIBCXX_ABI_VERSION to the default version so it'll only be generated if the change the default value (2 on Fuchsia, 1 everywhere else).

[smeenai]

Eric accepted on IRC.

libcxx/CMakeLists.txt

 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_SUPPORT_HEADERS "Install libc++ support headers." ON)
 cmake_dependent_option(LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY
         "Install libc++experimental.a" ON
         "LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY;LIBCXX_INSTALL_LIBRARY" OFF)
-set(LIBCXX_ABI_VERSION 1 CACHE STRING "ABI version of libc++.")
+if (FUCHSIA)
+  set(ABI_VERSION_DEFAULT 2)
+else()
+  set(ABI_VERSION_DEFAULT 1)
+endif()
+set(LIBCXX_ABI_VERSION ${ABI_VERSION_DEFAULT} CACHE STRING "ABI version of libc++.")
 option(LIBCXX_ABI_UNSTABLE "Unstable ABI of libc++." OFF)
 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_ABI_DEFINES "" CACHE STRING "A semicolon separated list of ABI macros to define in the site config header.")
 option(LIBCXX_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)
 
 if (NOT LIBCXX_ENABLE_SHARED AND NOT LIBCXX_ENABLE_STATIC)
   message(FATAL_ERROR "libc++ must be built as either a shared or static library.")
else()
       message(WARNING "Unsupported value of LLVM_USE_SANITIZER: ${LLVM_USE_SANITIZER}")
     endif()
   elseif(LLVM_USE_SANITIZER AND MSVC)
     message(WARNING "LLVM_USE_SANITIZER is not supported on this platform.")
   endif()
 endif()
 
 # Configuration file flags =====================================================
-if (NOT LIBCXX_ABI_VERSION EQUAL "1")
+if (NOT LIBCXX_ABI_VERSION EQUAL ABI_VERSION_DEFAULT)
   config_define(${LIBCXX_ABI_VERSION} _LIBCPP_ABI_VERSION)
 endif()
 config_define_if(LIBCXX_ABI_UNSTABLE _LIBCPP_ABI_UNSTABLE)
 config_define_if(LIBCXX_ABI_FORCE_ITANIUM _LIBCPP_ABI_FORCE_ITANIUM)
 config_define_if(LIBCXX_ABI_FORCE_MICROSOFT _LIBCPP_ABI_FORCE_MICROSOFT)
 
 config_define_if_not(LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE)
 config_define_if_not(LIBCXX_ENABLE_STDIN _LIBCPP_HAS_NO_STDIN)