[libunwind] [CMake] Allow building standalone without any llvm-config available

[mstorsjo]

Summary

This is the same as libcxxabi/libcxx do.

[phosek]

CMakeLists.txt

363

libcxx seems to be using a different condition: IS_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/test", should this be unified?

[mstorsjo]

CMakeLists.txt

363

Maybe, but there's more to it than that. libunwind's test/CMakeLists.txt will unconditionally try to do include(AddLLVM), which fails if LLVM_CMAKE_PATH isn't set. libcxx's test/CMakeLists.txt on the other hand will only try to do that if LIBCXX_INCLUDE_TESTS is defined, which it isn't by default.

There's lots of the llvm/cmake handling that seems to be quite outdated in libunwind compared to libcxxabi/libcxx, but I'm not really volunteering to unify that...

[rnk]

lgtm

CMakeLists.txt

elseif(LLVM_CONFIG_PATH)
     if(NOT HAD_ERROR)
       string(STRIP "${CONFIG_OUTPUT}" LLVM_CMAKE_PATH_FROM_LLVM_CONFIG)
       file(TO_CMAKE_PATH "${LLVM_CMAKE_PATH_FROM_LLVM_CONFIG}" LLVM_CMAKE_PATH)
     else()
       file(TO_CMAKE_PATH "${LLVM_BINARY_DIR}" LLVM_BINARY_DIR_CMAKE_STYLE)
       set(LLVM_CMAKE_PATH "${LLVM_BINARY_DIR_CMAKE_STYLE}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
     endif()
   else()
-    message(FATAL_ERROR "llvm-config not found and LLVM_MAIN_SRC_DIR not defined. "
-                        "Reconfigure with -DLLVM_CONFIG=path/to/llvm-config "
-                        "or -DLLVM_PATH=path/to/llvm-source-root.")
+    message(WARNING "UNSUPPORTED LIBUNWIND CONFIGURATION DETECTED: "
+                    "llvm-config not found and LLVM_MAIN_SRC_DIR not defined. "
   endif()
 
   if (EXISTS ${LLVM_CMAKE_PATH})
     list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_PATH}")
     include("${LLVM_CMAKE_PATH}/AddLLVM.cmake")
     include("${LLVM_CMAKE_PATH}/HandleLLVMOptions.cmake")
   else()
-    message(FATAL_ERROR "Not found: ${LLVM_CMAKE_PATH}")
+    message(WARNING "Not found: ${LLVM_CMAKE_PATH}")
   endif()
 
   set(PACKAGE_NAME libunwind)
   set(PACKAGE_VERSION 7.0.0svn)
   set(PACKAGE_STRING "${PACKAGE_NAME} ${PACKAGE_VERSION}")
   set(PACKAGE_BUGREPORT "[e-mail]")
 
   if (EXISTS ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)

 endif()
 
 add_subdirectory(src)
 
 if (LIBUNWIND_INCLUDE_DOCS)
   add_subdirectory(docs)
 endif()
 
+if (EXISTS ${LLVM_CMAKE_PATH})
   add_subdirectory(test)
+endif()