[libcxxabi] Provide options to set compiler/link flags for test programs.

[abidh]

Summary

Libunwind and libcxx have cmake variables to set the additional compiler and link flags needed to build a test program. The libcxxabi were missing those flags. This patch adds 'LIBCXXABI_TEST_LINKER_FLAGS' and 'LIBCXXABI_TEST_COMPILER_FLAGS' to fill this gap.

[ldionne]

We'd like to move away from going through CMake to set test-only variables, as it's not a great mechanism for doing so. Instead, please consider using a custom Lit config file like libcxx/test/configs/libcxx-trunk-shared.cfg.in, which allows you to customize how you run the test suite a lot more.

[ldionne]

In D86920#2249445, @ldionne wrote:

We'd like to move away from going through CMake to set test-only variables, as it's not a great mechanism for doing so. Instead, please consider using a custom Lit config file like libcxx/test/configs/libcxx-trunk-shared.cfg.in, which allows you to customize how you run the test suite a lot more.

To explain my point, what we're trying to avoid is to go through CMake in order to change specific Lit parameters. It's not a great model if for each Lit-related "customization point" we have, we also need to add a CMake variable and an entry in the lit.site.cfg.in file. It leads to bloated and complicated CMake files. Instead, modifying how you run lit directly is both more powerful and simpler.

[ldionne]

Please take a look at libcxx/test/configs/libcxx-trunk-shared.cfg.in and LIBCXX_TEST_CONFIG in CMake for how to customize exactly how you're running the test suite. This is a lot more powerful and simple than stringing options through CMake!

[abidh]

In D86920#2271948, @ldionne wrote:

Please take a look at libcxx/test/configs/libcxx-trunk-shared.cfg.in and LIBCXX_TEST_CONFIG in CMake for how to customize exactly how you're running the test suite. This is a lot more powerful and simple than stringing options through CMake!

Thanks. I found this variable and I tried using it with an out of tree file that was customized for my target and it works. This patch though does make CMake variable set consistent in libunwind/libcxxabi/libcxx. Otherwise we will have these variables in libunwind and libcxx and not in libcxxabi. If that is not important then I can abandon this patch.

[ldionne]

The approach to be taken for all runtime libraries is the one I described with specifying a custom config file. Please abandon!

libcxxabi/CMakeLists.txt

 option(LIBCXXABI_BUILD_32_BITS "Build 32 bit libc++abi." ${LLVM_BUILD_32_BITS})
 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_LIBRARY "Install the libc++abi library." ON)
 set(LIBCXXABI_TARGET_TRIPLE "" CACHE STRING "Target triple for cross compiling.")
 set(LIBCXXABI_GCC_TOOLCHAIN "" CACHE PATH "GCC toolchain for cross compiling.")
 set(LIBCXXABI_SYSROOT "" CACHE PATH "Sysroot for cross compiling.")
+set(LIBCXXABI_TEST_LINKER_FLAGS "" CACHE STRING
+    "Additional linker flags for test programs.")
+set(LIBCXXABI_TEST_COMPILER_FLAGS "" CACHE STRING
+    "Additional compiler flags for test programs.")
 set(LIBCXXABI_LIBCXX_LIBRARY_PATH "" CACHE PATH "The path to libc++ library.")
 set(LIBCXXABI_LIBRARY_VERSION "1.0" CACHE STRING
 "Version of libc++abi. This will be reflected in the name of the shared \
 library produced. For example, -DLIBCXXABI_LIBRARY_VERSION=x.y will \
 result in the library being named libc++abi.x.y.dylib, along with the \
 usual symlinks pointing to that.")
 
 # Default to building a shared library so that the default options still test

libcxxabi/test/lit.site.cfg.in

 config.enable_shared            = @LIBCXXABI_LINK_TESTS_WITH_SHARED_LIBCXX@
 config.enable_exceptions        = @LIBCXXABI_ENABLE_EXCEPTIONS@
 config.host_triple              = "@LLVM_HOST_TRIPLE@"
 config.target_triple            = "@TARGET_TRIPLE@"
 config.use_target               = bool("@LIBCXXABI_TARGET_TRIPLE@")
 config.sysroot                  = "@LIBCXXABI_SYSROOT@"
 config.gcc_toolchain            = "@LIBCXXABI_GCC_TOOLCHAIN@"
 config.cxx_ext_threads          = @LIBCXXABI_BUILD_EXTERNAL_THREAD_LIBRARY@
+config.test_linker_flags        = "@LIBCXXABI_TEST_LINKER_FLAGS@"
+config.test_compiler_flags      = "@LIBCXXABI_TEST_COMPILER_FLAGS@"
 
 config.pstl_src_root            = "@ParallelSTL_SOURCE_DIR@" if @LIBCXX_ENABLE_PARALLEL_ALGORITHMS@ else None
 config.pstl_obj_root            = "@ParallelSTL_BINARY_DIR@" if @LIBCXX_ENABLE_PARALLEL_ALGORITHMS@ else None
 
 # Code signing
 config.llvm_codesign_identity   = "@LLVM_CODESIGNING_IDENTITY@"
 
 site.addsitedir(os.path.join(config.libcxxabi_src_root, 'test'))