CMake Config files don't provide deprecated Module variables

[bebuch]

I try to build LLVM on Windows via MSVC with zlib-ng (in compatability mode), zstd and libxml2.

I have build these 3rdparty projects including there CMake Config files. I use a custom include install path. Therefor the old CMake Modules can't work for my build. I build LLVM with CMAKE_FIND_PACKAGE_PREFER_CONFIG=ON to used the installed project Config files.

I looks like LLVM uses some old style CMake variables including:

• ZLIB_INCLUDE_DIR=C:/usr/include/zlib_ng
• ZLIB_INCLUDE_DIRS=C:/usr/include/zlib_ng
• ZLIB_LIBRARY (missing, ZLIB_LIBRARIES is ZLIB::ZLIB)
• zstd_INCLUDE_DIR (missing)
• zstd_LIBRARY (missing)
• LIBXML2_INCLUDE_DIR=C:/usr/include/libxml2/libxml2
• LIBXML2_INCLUDE_DIRS=C:/usr/include/libxml2/libxml2
• LIBXML2_LIBRARY=debug;C:/usr/lib/libxml2d.lib;optimized;C:/usr/lib/libxml2.lib
• LIBXML2_LIBRARIES=debug;C:/usr/lib/libxml2d.lib;optimized;C:/usr/lib/libxml2.lib
• LIBXML2_DEFINITIONS=

As you can see zstd doesn't set any these old variables at all. They don't work with Multi-Config anyway.

Config files support Multi-Config, so *_LIBRARIES can't be set to the Debug or the Release lib file. zlib-ng sets it to ZLIB::ZLIB. libxml2 sets it to debug;C:/usr/lib/libxml2d.lib;optimized;C:/usr/lib/libxml2.lib. I think both isn't what LLVM expects.

Also the ZLIB check is broken, because ZLIB_LIBRARY is not set, ZLIB_LIBRARIES would work here.

llvm-project/llvm/cmake/config-ix.cmake

Lines 165 to 186 in 61ef286

	if(LLVM_ENABLE_ZLIB)
	if(LLVM_ENABLE_ZLIB STREQUAL FORCE_ON)
	find_package(ZLIB REQUIRED)
	elseif(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
	find_package(ZLIB)
	endif()
	if(ZLIB_FOUND)
	# Check if zlib we found is usable; for example, we may have found a 32-bit
	# library on a 64-bit system which would result in a link-time failure.
	cmake_push_check_state()
	list(APPEND CMAKE_REQUIRED_INCLUDES ${ZLIB_INCLUDE_DIRS})
	list(APPEND CMAKE_REQUIRED_LIBRARIES ${ZLIB_LIBRARY})
	check_symbol_exists(compress2 zlib.h HAVE_ZLIB)
	cmake_pop_check_state()
	if(LLVM_ENABLE_ZLIB STREQUAL FORCE_ON AND NOT HAVE_ZLIB)
	message(FATAL_ERROR "Failed to configure zlib")
	endif()
	endif()
	set(LLVM_ENABLE_ZLIB "${HAVE_ZLIB}")
	else()
	set(LLVM_ENABLE_ZLIB 0)
	endif()

The next problematic section seams to be:

llvm-project/llvm/cmake/modules/LLVMExternalProjectUtils.cmake

Lines 172 to 196 in 2334fd2

	set(DEFAULT_PASSTHROUGH_VARIABLES
	LibEdit_INCLUDE_DIRS
	LibEdit_LIBRARIES
	ZLIB_INCLUDE_DIR
	ZLIB_LIBRARY
	zstd_INCLUDE_DIR
	zstd_LIBRARY
	LIBXML2_LIBRARY
	LIBXML2_INCLUDE_DIR
	CURL_INCLUDE_DIR
	CURL_LIBRARY
	HTTPLIB_INCLUDE_DIR
	HTTPLIB_HEADER_PATH
	Python3_EXECUTABLE
	Python3_LIBRARIES
	Python3_INCLUDE_DIRS
	Python3_RPATH
	)
	foreach(variable ${DEFAULT_PASSTHROUGH_VARIABLES})
	get_property(is_value_set CACHE ${variable} PROPERTY VALUE SET)
	if(${is_value_set})
	get_property(value CACHE ${variable} PROPERTY VALUE)
	list(APPEND CMAKE_CACHE_DEFAULT_ARGS "-D${variable}:STRING=${value}")
	endif()
	endforeach()

This looks to me, like a forwarding of arguments to a subsequent call.

I think this may be the reason for this error in my build:

loading initial cache file C:/TechnoTeam/develop/usr/build/llvm/projects/runtimes/tmp/runtimes-cache-Release.cmake
-- Performing bootstrapping runtimes build.
-- Could NOT find ZLIB (missing: ZLIB_INCLUDE_DIR)
-- Could NOT find zstd (missing: zstd_INCLUDE_DIR)
-- Could NOT find LibXml2 (missing: LIBXML2_INCLUDE_DIR)
-- Could NOT find ZLIB (missing: ZLIB_INCLUDE_DIR)
-- Could NOT find zstd (missing: zstd_INCLUDE_DIR)
-- Could NOT find LibXml2 (missing: LIBXML2_INCLUDE_DIR)
CMake Error at C:/temp/tt/env/share/cmake-3.31/Modules/FindPackageHandleStandardArgs.cmake:233 (message):
  Could NOT find Python3 (missing: Python3_EXECUTABLE Interpreter)
Call Stack (most recent call first):
  C:/temp/tt/env/share/cmake-3.31/Modules/FindPackageHandleStandardArgs.cmake:603 (_FPHSA_FAILURE_MESSAGE)
  C:/temp/tt/env/share/cmake-3.31/Modules/FindPython/Support.cmake:4002 (find_package_handle_standard_args)
  C:/temp/tt/env/share/cmake-3.31/Modules/FindPython3.cmake:602 (include)
  CMakeLists.txt:180 (find_package)

I am investigating this further and will add to this issue.