[PATCH] [libcxx] Add support for linking libc++ against a static ABI library.

[Saleem Abdulrasool]

================
Comment at: CMakeLists.txt:64
@@ -63,2 +63,3 @@
 option(LIBCXX_INSTALL_SUPPORT_HEADERS "Install libc++ support headers." ON)
+option(LIBCXX_ENABLE_STATIC_ABI_LIBRARY "Statically link the ABI library" OFF)
 set(LIBCXX_SYSROOT "" CACHE STRING "Use alternate sysroot.")
----------------
Maybe this should be something like LIBCXX_STATIC_LIBCXXABI.  Otherwise, we need checks for the case that we are trying to use libsupc++/libcxxrt and don't have a static version available.

================
Comment at: CMakeLists.txt:74
@@ +73,3 @@
+  if (APPLE)
+    message(FATAL_ERROR "LIBCXX_ENABLE_STATIC_ABI_LIBRARY is not supported on OS X")
+  else()
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Any reason to not support this on Darwin really?  I think that we can build a DSO for libc++ and just grab the $<TARGET_OBJECTS:c++abi> (or a static archive/library).

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Comment at: cmake/Modules/HandleLibCXXABI.cmake:85
@@ -82,1 +84,3 @@
+        set(CXXABI_LIBNAME cxxabi_shared)
+    endif()
     set(LIBCXX_LIBCPPABI_VERSION "2" PARENT_SCOPE)
----------------
EricWF wrote:
> compnerd wrote:
> > Why do you change the name of the library, the name should stay the same, its the extension that changes (and I believe should be implicit based on add_library).
> The actual library name ('libc++abi.so' or 'libc++abi.a') doesn't change. These are CMake target names for when libc++abi and libc++ are being built intree together.
Yeah, thats what happens when you look at a patch set out of order :-p.

================
Comment at: test/CMakeLists.txt:47
@@ -46,1 +46,3 @@
   pythonize_bool(LIBCXX_ENABLE_MONOTONIC_CLOCK)
+  # The tests shouldn't link to any ABI library when it has been linked into
+  # libc++ statically.
----------------
EricWF wrote:
> compnerd wrote:
> > Can you explain why this is correct?  The tests are meant to test libc++abi.  They should link to it either statically or dynamically as built.  The libc++ tests however, should not.
> Because when libc++ statically links to libc++abi then all of the symbols from libc++abi should be available via libc++. If we don't do this and always link the tests to libc++abi then it could hide errors where libc++ doesn't properly expose the required symbols.
Agreed, but the libc++abi tests shouldn't try to pull the symbols indirectly from libc++.  They should have direct access to libc++abi symbols.

http://reviews.llvm.org/D8017

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