[CMake][compiler-rt] Provide a dedicated option for LLVM unwinder

[phosek]

Summary

This allows configuring LLVM unwinder separately from the C++ library
matching how we configure it in libcxx.

This also applies changes made to libunwind+libcxxabi+libcxx in D113253
to compiler-rt.

[mstorsjo]

LGTM

(Why don't the sanitizers default to any of the *-commits mailing lists as subscribers?)

[mstorsjo]

compiler-rt/CMakeLists.txt

528

I presume we should only do this if we actually know we're linking against a libunwind that is built in the same cmake invocation, i.e. either of the TARGET unwind_* OR HAVE_LIBUNWIND cases below, otherwise this does break things.

[phosek]

compiler-rt/CMakeLists.txt

528

Yes, I hope this could be more cleanly addressed by D126909.

[mstorsjo]

compiler-rt/CMakeLists.txt

514

This todo refers to this change itself.

528

Hmm, this feels a bit nonobvious, when this here isn't directly related to the COMPILER_RT_USE_LLVM_UNWINDER variable. Is it the case that this only gets called when COMPILER_RT_USE_LLVM_UNWINDER is true, or can you end up with other kinds of mismatches?

[phosek]

compiler-rt/CMakeLists.txt

528

I removed it from this change. Prior to this change, C++ ABI and unwinder in compiler-rt is controlled by a single option, but that's causing issues. This change introduces a separate option for controlling the unwinder. I'm also working on another change that will introduce a new option for controlling C++ library. When those land, I think we should deprecate and remove the original flag.

[phosek]

@mstorsjo let me know if this looks good to you, I tested this locally and it seems to be working fine.

[mstorsjo]

The changes left in this patch seem fine to me now!

compiler-rt/CMakeLists.txt

if(CMAKE_CONFIGURATION_TYPES)
   set(CMAKE_CFG_RESOLVED_INTDIR "${CMAKE_CFG_INTDIR}/")
 else()
   set(CMAKE_CFG_RESOLVED_INTDIR "")
 endif()
 
 include(SetPlatformToolchainTools)
 include(base-config-ix)
 include(CompilerRTUtils)
+include(CMakeDependentOption)
 
 option(COMPILER_RT_BUILD_BUILTINS "Build builtins" ON)
 mark_as_advanced(COMPILER_RT_BUILD_BUILTINS)
 option(COMPILER_RT_BUILD_CRT "Build crtbegin.o/crtend.o" ON)
 mark_as_advanced(COMPILER_RT_BUILD_CRT)
 option(COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY "Use eh_frame in crtbegin.o/crtend.o" ON)
 mark_as_advanced(COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY)
 option(COMPILER_RT_BUILD_SANITIZERS "Build sanitizers" ON)

 
 # This needs to be a full C++ library for linking gtest and unit tests.
 set(SANITIZER_TEST_CXX "default" CACHE STRING
     "Specify C++ library to use for tests.")
 set(CXXLIBS none default libstdc++ libc++)
 set_property(CACHE SANITIZER_TEST_CXX PROPERTY STRINGS ;${CXXLIBS})
 handle_default_cxx_lib(SANITIZER_TEST_CXX)
 
+option(COMPILER_RT_USE_LLVM_UNWINDER "Use the LLVM unwinder." OFF)
+cmake_dependent_option(COMPILER_RT_ENABLE_STATIC_UNWINDER
+  "Statically link the LLVM unwinder." OFF
+  "COMPILER_RT_USE_LLVM_UNWINDER" OFF)
+
 set(DEFAULT_SANITIZER_USE_STATIC_LLVM_UNWINDER OFF)
 if (FUCHSIA)
   set(DEFAULT_SANITIZER_USE_STATIC_LLVM_UNWINDER ON)
 elseif (DEFINED LIBUNWIND_ENABLE_SHARED AND NOT LIBUNWIND_ENABLE_SHARED)
   set(DEFAULT_SANITIZER_USE_STATIC_LLVM_UNWINDER ON)
 endif()
 
 option(SANITIZER_USE_STATIC_LLVM_UNWINDER

 # Remove -stdlib= which is unused when passing -nostdinc++...
 string(REGEX MATCHALL "-stdlib=[a-zA-Z+]*" stdlib_flag "${CMAKE_CXX_FLAGS}")
 string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 # ...we need it to build some runtimes and tests so readd it where appropriate.
 list(APPEND COMPILER_RT_COMMON_CFLAGS ${stdlib_flag})
 list(APPEND COMPILER_RT_COMMON_LINK_FLAGS ${stdlib_flag})
 
+if(COMPILER_RT_USE_LLVM_UNWINDER)
+  # TODO: set --unwindlib=none after https://reviews.llvm.org/D115674 lands.
+  if (COMPILER_RT_ENABLE_STATIC_UNWINDER)
+    set(unwinder_target unwind_static)
+  else()
+    set(unwinder_target unwind_shared)
+  endif()
+  list(APPEND SANITIZER_CXX_ABI_LIBRARIES "$<$<TARGET_EXISTS:${unwind_target}>:$<TARGET_LINKER_FILE:${unwind_target}>>")
+endif()
+
 macro(append_libcxx_libs var)
   if (${var}_INTREE)
+    # If we're linking directly against the libunwind that we're building
+    # in the same invocation, don't try to link in the toolchain's
+    # default libunwind (which may be missing still).
+    append_list_if(CXX_SUPPORTS_UNWINDLIB_NONE_FLAG --unwindlib=none SANITIZER_COMMON_LINK_FLAGS)
+
     if (SANITIZER_USE_STATIC_LLVM_UNWINDER AND (TARGET unwind_static OR HAVE_LIBUNWIND))
       list(APPEND ${var}_LIBRARIES unwind_static)
     elseif (TARGET unwind_shared OR HAVE_LIBUNWIND)
       list(APPEND ${var}_LIBRARIES unwind_shared)
     endif()
 
     if (SANITIZER_USE_STATIC_CXX_ABI AND (TARGET cxxabi_static OR HAVE_LIBCXXABI))
       list(APPEND ${var}_LIBRARIES cxxabi_static)

compiler-rt/cmake/config-ix.cmake

 include(CMakePushCheckState)
 include(LLVMCheckCompilerLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckIncludeFiles)
 include(CheckLibraryExists)
+include(LLVMCheckCompilerLinkerFlag)
 include(CheckSymbolExists)
 include(TestBigEndian)
 
+# The compiler driver may be implicitly trying to link against libunwind.
+# This is normally ok (libcxx relies on an unwinder), but if libunwind is
+# built in the same cmake invocation as compiler-rt and we're using the
+# in tree version of runtimes, we'd be linking against the just-built
+# libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly
+# built libunwind isn't installed yet). For those cases, it'd be good to
+# link with --uwnindlib=none. Check if that option works.
+llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
+
 check_library_exists(c fopen "" COMPILER_RT_HAS_LIBC)
 if (COMPILER_RT_USE_BUILTINS_LIBRARY)
   include(HandleCompilerRT)
   find_compiler_rt_library(builtins COMPILER_RT_BUILTINS_LIBRARY
                            FLAGS ${SANITIZER_COMMON_FLAGS})
   # TODO(PR51389): We should check COMPILER_RT_BUILTINS_LIBRARY and report an
   # error if the value is NOTFOUND rather than silenty continuing but we first
   # need to fix find_compiler_rt_library on Darwin.

compiler-rt/lib/scudo/standalone/CMakeLists.txt

 set(SCUDO_LINK_FLAGS)
 
 list(APPEND SCUDO_LINK_FLAGS -Wl,-z,defs,-z,now,-z,relro)
 
 list(APPEND SCUDO_LINK_FLAGS -ffunction-sections -fdata-sections -Wl,--gc-sections)
 
 # We don't use the C++ standard library, so avoid including it by mistake.
 append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ SCUDO_LINK_FLAGS)
+append_list_if(CXX_SUPPORTS_UNWINDLIB_NONE_FLAG --unwindlib=none SCUDO_LINK_FLAGS)
 
 if(ANDROID)
   list(APPEND SCUDO_CFLAGS -fno-emulated-tls)
 
 # Put the shared library in the global group. For more details, see
 # android-changes-for-ndk-developers.md#changes-to-library-search-order
   append_list_if(COMPILER_RT_HAS_Z_GLOBAL -Wl,-z,global SCUDO_LINK_FLAGS)
 endif()