[libcxx][libcxxabi] CMAKE_REQUIRED_FLAGS is a string, not a list

[nehaljwani]

Summary

When libcxx or libcxxabi is built with -DLLVM_USE_SANITIZER=MemoryWithOrigins
and -DLIBCXX[ABI]_USE_COMPILER_RT=ON, all of the LIBCXX[ABI]_SUPPORTS_*_FLAG
checks fail, since the value of CMAKE_REQUIRED_FLAGS is not set correctly.

Bugzilla: https://bugs.llvm.org/show_bug.cgi?id=51774

[nehaljwani]

Added link to BZ in commit message

[compnerd]

libcxx/cmake/config-ix.cmake

43

This is changing the behavior. CMAKE_REQUIRED_LIBRARIES was being set here previously and that is correct. Unlike CMAKE_REQUIRED_FLAGS, that is a ; delimited list.

libcxxabi/cmake/config-ix.cmake

33

Similar.

[nehaljwani]

Remove changes that touch CMAKE_REQUIRED_LIBRARIES

[Mordante]

Can you add a more verbose description? The current commit message is a bit short.
It seems buildkite has a lot of failures. Looking at the used pipelines I miss a lot of them. Is your patch against a recent version of main?

[ldionne]

LGTM if CI passes.

[nehaljwani]

Added more information in the commit message, rebased over latest origin/main

[Mordante]

In D109342#2989553, @nehaljwani wrote:

Added more information in the commit message, rebased over latest origin/main

Thanks Buildkite now looks good. I don't see a new description in this patch. Did you only update it in your commit message?

[nehaljwani]

I've updated the summary of this differential as well. Is that what you were referring to, @Mordante ?

[Mordante]

In D109342#2990516, @nehaljwani wrote:

I've updated the summary of this differential as well. Is that what you were referring to, @Mordante ?

Yes thanks. Especially nice to know this fixes a bug.

Do you need somebody to commit his for you? If so please provide "your name" <[e-mail]> so somebody can commit on your behalf.

[nehaljwani]

I don't have any commit rights. Here is the info you need:

$ git show | grep Author:
Author: Nehal J Wani <[e-mail]>

libcxx/cmake/config-ix.cmake

 # configuration checks to avoid spurious link errors.
 check_c_compiler_flag(-nodefaultlibs LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
 if (LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
   if (LIBCXX_HAS_C_LIB)
     list(APPEND CMAKE_REQUIRED_LIBRARIES c)
   endif ()
   if (LIBCXX_USE_COMPILER_RT)
-    list(APPEND CMAKE_REQUIRED_FLAGS -rtlib=compiler-rt)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -rtlib=compiler-rt")
     find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY)
     list(APPEND CMAKE_REQUIRED_LIBRARIES "${LIBCXX_BUILTINS_LIBRARY}")
   elseif (LIBCXX_HAS_GCC_LIB)
     list(APPEND CMAKE_REQUIRED_LIBRARIES gcc)
   elseif (LIBCXX_HAS_GCC_S_LIB)
     list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s)
   endif ()
   if (MINGW)
     # Mingw64 requires quite a few "C" runtime libraries in order for basic
     # programs to link successfully with -nodefaultlibs.

libcxxabi/cmake/config-ix.cmake

 # configuration checks to avoid spurious link errors.
 check_c_compiler_flag(-nodefaultlibs LIBCXXABI_HAS_NODEFAULTLIBS_FLAG)
 if (LIBCXXABI_HAS_NODEFAULTLIBS_FLAG)
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
   if (LIBCXXABI_HAS_C_LIB)
     list(APPEND CMAKE_REQUIRED_LIBRARIES c)
   endif ()
   if (LIBCXXABI_USE_COMPILER_RT)
-    list(APPEND CMAKE_REQUIRED_FLAGS -rtlib=compiler-rt)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -rtlib=compiler-rt")
     find_compiler_rt_library(builtins LIBCXXABI_BUILTINS_LIBRARY)
     list(APPEND CMAKE_REQUIRED_LIBRARIES "${LIBCXXABI_BUILTINS_LIBRARY}")
   else ()
     if (LIBCXXABI_HAS_GCC_S_LIB)
       list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s)
     endif ()
     if (LIBCXXABI_HAS_GCC_LIB)
       list(APPEND CMAKE_REQUIRED_LIBRARIES gcc)
     endif ()
   endif ()