[CMake] Filter libc++abi and libunwind from runtimes build in MSVC

[phosek]

Summary

These don't build in MSVC at the moment, so filter these out altogether
from the list of runtimes and print a warning.

[phosek]

I'm not sure if there's a better way. I cannot remove these from LLVM_ENABLE_RUNTIMES since I still want to build these for other targets, but I don't want these for Windows because they break the build.

[mstorsjo]

Just for clarity, can you clarify in the subject that this is for windows/msvc (as I see in the code that you keep allowing building them for mingw - thanks for that!).

(I still only build these libs as standalone builds myself, but maybe I'll have time to try integrated building at some point.)

[mstorsjo]

Thanks!

[smeenai]

We added support for overriding LLVM_ENABLE_RUNTIMES on a per-target basis for this exact reason in D67195. Does that work for you?

(I want to generalize that support a bit, but it should already work for LLVM_ENABLE_RUNTIMES.)

[phosek]

In D73812#1855632, @smeenai wrote:

We added support for overriding LLVM_ENABLE_RUNTIMES on a per-target basis for this exact reason in D67195. Does that work for you?

(I want to generalize that support a bit, but it should already work for LLVM_ENABLE_RUNTIMES.)

Not out-of-the-box because that filter is only used for explicit targets, not for the "default" builtins and runtimes (i.e. host) which is what we currently use on Windows and Darwin.

[smeenai]

In that case, looks good with the condition changed to MSVC.

llvm/runtimes/CMakeLists.txt

30–31

I think MSVC is a better condition here than WIN32 AND NOT MINGW, since libunwind and libc++abi aren't compatible with the MSVC ABI.

[phosek]

llvm/runtimes/CMakeLists.txt

30–31

Done, I've also added a warning so it's easier to spot in the output.

[vvereschaka]

Hello @phosek,

these changes break the ARM cross builders on Windows:
http://lab.llvm.org:8011/builders/llvm-clang-win-x-armv7l/builds/4240

also it suppresses building of the libraries on the Aarch64 cross builder http://lab.llvm.org:8011/builders/llvm-clang-win-x-aarch64

We use "just built" clang toolchain to build the runtime/builtin libraries there. These changes do not allow using the toolchain in case it was built by MSVC.

Would you fix it or revert the commit?

[vvereschaka]

Hello @phosek,

the builders are broken for the third day in a row.
Sorry, but I'm going to revert this commit.

[phosek]

In D73812#1864675, @vvereschaka wrote:

Hello @phosek,

the builders are broken for the third day in a row.
Sorry, but I'm going to revert this commit.

No worries and sorry about the late response, I missed your earlier message. I'll take a look into this issue.

llvm/runtimes/CMakeLists.txt

 # Side-by-side subprojects layout.
 set(LLVM_ALL_RUNTIMES "libcxx;libcxxabi;libunwind;compiler-rt")
 set(LLVM_ENABLE_RUNTIMES "" CACHE STRING
   "Semicolon-separated list of runtimes to build (${LLVM_ALL_RUNTIMES}), or \"all\".")
 if(LLVM_ENABLE_RUNTIMES STREQUAL "all" )
   set(LLVM_ENABLE_RUNTIMES ${LLVM_ALL_RUNTIMES})
 endif()
 foreach(proj ${LLVM_ENABLE_RUNTIMES})
+  # TODO: libunwind and libcxxabi don't currently build on Windows so filter them out.
+  if(MSVC AND ("${proj}" MATCHES "libunwind|libcxxabi"))
+    message(WARNING "Skipping ${proj} which is not supported in MSVC yet")
+    continue()
+  endif()
+
   set(proj_dir "${CMAKE_CURRENT_SOURCE_DIR}/../../${proj}")
   if(IS_DIRECTORY ${proj_dir} AND EXISTS ${proj_dir}/CMakeLists.txt)
     list(APPEND runtimes ${proj_dir})
   else()
     message(FATAL_ERROR "LLVM_ENABLE_RUNTIMES requests ${proj} but directory not found: ${proj_dir}")
   endif()
   string(TOUPPER "${proj}" canon_name)
   STRING(REGEX REPLACE "-" "_" canon_name ${canon_name})