Recommit r290839 - Fix configuring and building libc++ w/o an ABI library.

This patch re-commits a previous attempt to support building libc++ w/o
an ABI library. That patch was originally reverted because:

1) It forgot to teach the test suite about "default" ABI libraries.

2) Some LLVM builders don't clear the CMake cache between builds. The previous
   patch caused those builders to fail since their old cache entry for
   LIBCXX_CXX_ABI="" is no longer valid.

The updated patch addresses both issues. It works around (2) by adding
a hack to force the builders to update their cache entries. The hack will
be removed shortly once all LLVM builders have run.

Original commit message
-----------------------

Typically libc++ uses libc++abi or libcxxrt to provide the ABI and runtime bits
of the C++ STL. However we also support building w/o an ABI library entirely.
This patch fixes building libc++ w/o an ABI library (and incorporates the
`~type_info()` fix in D28211).

The main changes in this patch are:

1) Add `-DLIBCXX_CXX_ABI=default` instead of using the empty string to mean "default".
2) Fix CMake bits which treated "none" as "default" on OS X.
3) Teach the source files to respect `-D_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY`.
4) Define ~type_info() when _LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY is defined.

Unfortunately this patch doesn't help clean up the macro mess that we use to
configure for different ABI libraries.

llvm-svn: 290849

1 files changed, 8 insertions, 3 deletions

diff --git a/libcxx/cmake/Modules/HandleLibCXXABI.cmake b/libcxx/cmake/Modules/HandleLibCXXABI.cmake
index 39f2aa575b4..df3b4f9f5cd 100644
--- a/libcxx/cmake/Modules/HandleLibCXXABI.cmake
+++ b/libcxx/cmake/Modules/HandleLibCXXABI.cmake
@@ -102,9 +102,14 @@ elseif ("${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "libcxxrt")
   setup_abi_lib("-DLIBCXXRT"
     "cxxrt" "cxxabi.h;unwind.h;unwind-arm.h;unwind-itanium.h" ""
     )
-elseif (NOT "${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "none")
+elseif ("${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "none")
+  list(APPEND LIBCXX_COMPILE_FLAGS "-D_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY")
+elseif ("${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "default")
+  # Nothing TODO
+else()
   message(FATAL_ERROR
-    "Currently libstdc++, libsupc++, libcxxabi, libcxxrt and none are "
-    "supported for c++ abi."
+    "Unsupported c++ abi: '${LIBCXX_CXX_ABI_LIBNAME}'. \
+     Currently libstdc++, libsupc++, libcxxabi, libcxxrt, default and none are
+     supported for c++ abi."
     )
 endif ()