[CMake] Ensure `CLANG_RESOURCE_DIR` is respected

[paperchalice]

Summary

This patch ensures all resources are installed into CLANG_RESOURCE_DIR.
Fixes: https://github.com/llvm/llvm-project/issues/59726

[paperchalice]

Use LLVM_LIBRARY_OUTPUT_INTDIR.

[mgorny]

While the general direction seems sound, I suspect this may be a real PITA given that for us:

-DCLANG_RESOURCE_DIR="../../../../lib/clang/${LLVM_MAJOR}"

I'm going to try and see later throughout the week if it's possible to keep that working with this patch.

[mgorny]

Ok, this turned out to be surprisingly painless, at least within our packaging.

However, I'd prefer if someone more experienced looked at the CMake changes.

[MaskRay]

The CMake part of this patch improves the matter. Manually constructed resource dir (many duplicates) string is replace with a library function call.

However, the introduced conditions in C++ code like

std::string path_to_clang_dir = std::string(CLANG_RESOURCE_DIR).empty()
                                    ? "/foo/bar/" LLDB_INSTALL_LIBDIR_BASENAME
                                      "/clang/" CLANG_VERSION_MAJOR_STRING
                                    : "/foo/bar/bin/" CLANG_RESOURCE_DIR;

makes me uncomfortable.

I wish that we can just replace all manually constructed CLANG_INSTALL_LIBDIR_BASENAME "/clang/" CLANG_VERSION_MAJOR_STRING with a simple CLANG_RESOURCE_DIR which is guaranteed to be non-empty.

edeaf16f2c2f02d6e43312d48d26d354d87913f3 (2011) added the CMake variable CLANG_RESOURCE_DIR but did not explain why.
In the long term, the CMake variable CLANG_RESOURCE_DIR probably should be removed.

[paperchalice]

In D141907#4094748, @MaskRay wrote:

The CMake part of this patch improves the matter. Manually constructed resource dir (many duplicates) string is replace with a library function call.

However, the introduced conditions in C++ code like

std::string path_to_clang_dir = std::string(CLANG_RESOURCE_DIR).empty()
                                    ? "/foo/bar/" LLDB_INSTALL_LIBDIR_BASENAME
                                      "/clang/" CLANG_VERSION_MAJOR_STRING
                                    : "/foo/bar/bin/" CLANG_RESOURCE_DIR;

makes me uncomfortable.

I wish that we can just replace all manually constructed CLANG_INSTALL_LIBDIR_BASENAME "/clang/" CLANG_VERSION_MAJOR_STRING with a simple CLANG_RESOURCE_DIR which is guaranteed to be non-empty.

edeaf16f2c2f02d6e43312d48d26d354d87913f3 (2011) added the CMake variable CLANG_RESOURCE_DIR but did not explain why.
In the long term, the CMake variable CLANG_RESOURCE_DIR probably should be removed.

clang::driver::Driver::GetResourcesPath would be a better choice.

[phosek]

cmake/Modules/GetClangResourceDir.cmake

18

This variable is only used once on the following line, I'd just inline it which is more idiomatic.

19

It's more idiomatic to parse arguments at the start of the function.

19

This is just a nit, but we usually use a prefix like ARGS to make it clear that these are input arguments.

[paperchalice]

• Use clang::driver::Driver::GetResourcesPath
• Use ARG as prefix

[paperchalice]

Ping.

lldb/source/Plugins/ExpressionParser/Clang/ClangHost.cpp

56

Should be "${CMAKE_INSTALL_BINDIR}/lldb" here, but need another variable in config.h.