[libcxx-commits] [PATCH] D113253: [runtimes] Fix building initial libunwind+libcxxabi+libcxx with compiler implied -lunwind

[Martin Storsjö via Phabricator via libcxx-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG529a79302bf3: Reapply #2 of [runtimes] Fix building initial libunwind+libcxxabi+libcxx with… (authored by mstorsjo).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D113253/new/

https://reviews.llvm.org/D113253

Files:
  libcxx/CMakeLists.txt
  libcxx/cmake/config-ix.cmake
  runtimes/CMakeLists.txt


Index: runtimes/CMakeLists.txt
===================================================================
--- runtimes/CMakeLists.txt
+++ runtimes/CMakeLists.txt
@@ -32,6 +32,8 @@
 list(INSERT CMAKE_MODULE_PATH 0
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules"
+  "${CMAKE_CURRENT_SOURCE_DIR}/../cmake"
+  "${CMAKE_CURRENT_SOURCE_DIR}/../cmake/Modules"
   "${CMAKE_CURRENT_SOURCE_DIR}/../llvm/cmake"
   "${CMAKE_CURRENT_SOURCE_DIR}/../llvm/cmake/modules"
 )
@@ -84,14 +86,29 @@
 set(LLVM_PATH ${CMAKE_CURRENT_SOURCE_DIR}/../llvm)
 
 include(CheckLibraryExists)
+include(CheckLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 
+
+check_c_compiler_flag("" LLVM_RUNTIMES_LINKING_WORKS)
+if (NOT LLVM_RUNTIMES_LINKING_WORKS)
+  # The compiler driver may be implicitly trying to link against libunwind, which
+  # might not work if libunwind doesn't exist yet. Try to check if
+  # --unwindlib=none is supported, and use that if possible.
+  # Don't add this if not necessary to fix linking, as it can break using
+  # e.g. ASAN/TSAN.
+  llvm_check_linker_flag("--unwindlib=none" LLVM_RUNTIMES_SUPPORT_UNWINDLIB_NONE_FLAG)
+  if (LLVM_RUNTIMES_SUPPORT_UNWINDLIB_NONE_FLAG)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --unwindlib=none")
+  endif()
+endif()
+
 # Disable use of the installed C++ standard library when building runtimes.
 # Check for -nostdlib++ first; if there's no C++ standard library yet,
 # all check_cxx_compiler_flag commands will fail until we add -nostdlib++
 # (or -nodefaultlibs).
-check_c_compiler_flag(-nostdlib++ LLVM_RUNTIMES_SUPPORT_NOSTDLIBXX_FLAG)
+llvm_check_linker_flag(-nostdlib++ LLVM_RUNTIMES_SUPPORT_NOSTDLIBXX_FLAG)
 if (LLVM_RUNTIMES_SUPPORT_NOSTDLIBXX_FLAG)
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
 endif()
Index: libcxx/cmake/config-ix.cmake
===================================================================
--- libcxx/cmake/config-ix.cmake
+++ libcxx/cmake/config-ix.cmake
@@ -1,9 +1,22 @@
 include(CMakePushCheckState)
 include(CheckLibraryExists)
+include(CheckLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckCSourceCompiles)
 
+# 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 libcxx and we've got
+# LIBCXXABI_USE_LLVM_UNWINDER set, 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_linker_flag("--unwindlib=none" LIBCXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
+if (LIBCXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --unwindlib=none")
+endif()
+
 if(WIN32 AND NOT MINGW)
   # NOTE(compnerd) this is technically a lie, there is msvcrt, but for now, lets
   # let the default linking take care of that.
Index: libcxx/CMakeLists.txt
===================================================================
--- libcxx/CMakeLists.txt
+++ libcxx/CMakeLists.txt
@@ -765,6 +765,13 @@
     target_add_link_flags_if_supported(${target} PRIVATE "/nodefaultlib")
   endif()
 
+  if (LIBCXX_SUPPORTS_UNWINDLIB_NONE_FLAG AND LIBCXXABI_USE_LLVM_UNWINDER)
+    # 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).
+    target_add_link_flags_if_supported(${target} PRIVATE "--unwindlib=none")
+  endif()
+
   if (LIBCXX_HAS_SYSTEM_LIB)
     target_link_libraries(${target} PRIVATE System)
   endif()


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