[libcxx-commits] [libcxx] 7c3d19a - [runtimes] Fix building initial libunwind+libcxxabi+libcxx with compiler implied -lunwind
Martin Storsjö via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Nov 16 13:06:32 PST 2021
Author: Martin Storsjö
Date: 2021-11-16T23:04:06+02:00
New Revision: 7c3d19ab7bcb79636bd65ee55a0fefef224fcb25
URL: https://github.com/llvm/llvm-project/commit/7c3d19ab7bcb79636bd65ee55a0fefef224fcb25
DIFF: https://github.com/llvm/llvm-project/commit/7c3d19ab7bcb79636bd65ee55a0fefef224fcb25.diff
LOG: [runtimes] Fix building initial libunwind+libcxxabi+libcxx with compiler implied -lunwind
This does mostly the same as D112126, but for the runtimes cmake files.
Most of that is straightforward, but the interdependency between
libcxx and libunwind is tricky:
Libunwind is built at the same time as libcxx, but libunwind is not
installed yet. LIBCXXABI_USE_LLVM_UNWINDER makes libcxx link directly
against the just-built libunwind, but the compiler implicit -lunwind
isn't found. This patch avoids that by adding --unwindlib=none if
supported, if we are going to link explicitly against a newly built
unwinder anyway.
Differential Revision: https://reviews.llvm.org/D113253
Added:
Modified:
libcxx/CMakeLists.txt
libcxx/cmake/config-ix.cmake
runtimes/CMakeLists.txt
Removed:
################################################################################
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 5ab8a30d57e96..dafc6ce2cc496 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -773,6 +773,13 @@ function(cxx_link_system_libraries target)
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(${target} PRIVATE System)
endif()
diff --git a/libcxx/cmake/config-ix.cmake b/libcxx/cmake/config-ix.cmake
index 8ca8b14151dfa..167ea812ba574 100644
--- a/libcxx/cmake/config-ix.cmake
+++ b/libcxx/cmake/config-ix.cmake
@@ -1,9 +1,22 @@
include(CMakePushCheckState)
include(CheckLibraryExists)
+include(CheckLinkerFlag)
include(CheckCCompilerFlag)
include(CheckCXXCompilerFlag)
include(CheckCSourceCompiles)
+# The compiler driver may be implicitly trying to link against libunwind.
+# This is normally ok (libcxx relies on an unwinder), but if libunwind is
+# built in the same cmake invocation as libcxx and we've got
+# LIBCXXABI_USE_LLVM_UNWINDER set, we'd be linking against the just-built
+# libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly
+# built libunwind isn't installed yet). For those cases, it'd be good to
+# link with --uwnindlib=none. Check if that option works.
+llvm_check_linker_flag("--unwindlib=none" LIBCXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
+if (LIBCXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
+ set(CMAKE_REQUIRED_FLAGS "${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.
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 85b865ea078e3..2989057c9135f 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -1,6 +1,21 @@
# This file handles building LLVM runtime sub-projects.
cmake_minimum_required(VERSION 3.13.4)
-project(Runtimes C CXX ASM)
+
+# Add path for custom and the LLVM build's modules to the CMake module path.
+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"
+)
+
+# We may have an incomplete toolchain - do language support tests without
+# linking.
+include(EnableLanguageNolink)
+project(Runtimes LANGUAGES NONE)
+llvm_enable_language_nolink(C CXX ASM)
set(LLVM_ALL_RUNTIMES "compiler-rt;libc;libcxx;libcxxabi;libunwind;openmp")
set(LLVM_ENABLE_RUNTIMES "" CACHE STRING
@@ -28,14 +43,6 @@ endfunction()
find_package(LLVM PATHS "${LLVM_BINARY_DIR}" NO_DEFAULT_PATH NO_CMAKE_FIND_ROOT_PATH)
find_package(Clang PATHS "${LLVM_BINARY_DIR}" NO_DEFAULT_PATH NO_CMAKE_FIND_ROOT_PATH)
-# Add path for custom and the LLVM build's modules to the CMake module path.
-list(INSERT CMAKE_MODULE_PATH 0
- "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
- "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules"
- "${CMAKE_CURRENT_SOURCE_DIR}/../llvm/cmake"
- "${CMAKE_CURRENT_SOURCE_DIR}/../llvm/cmake/modules"
-)
-
set(LLVM_THIRD_PARTY_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../third-party")
function(get_compiler_rt_path path)
@@ -88,14 +95,29 @@ if(APPLE)
endif()
include(CheckLibraryExists)
+include(CheckLinkerFlag)
include(CheckCCompilerFlag)
include(CheckCXXCompilerFlag)
+
+check_c_compiler_flag("" LLVM_RUNTIMES_LINKING_WORKS)
+if (NOT LLVM_RUNTIMES_LINKING_WORKS)
+ # The compiler driver may be implicitly trying to link against libunwind, which
+ # might not work if libunwind doesn't exist yet. Try to check if
+ # --unwindlib=none is supported, and use that if possible.
+ # Don't add this if not necessary to fix linking, as it can break using
+ # e.g. ASAN/TSAN.
+ llvm_check_linker_flag("--unwindlib=none" LLVM_RUNTIMES_SUPPORT_UNWINDLIB_NONE_FLAG)
+ if (LLVM_RUNTIMES_SUPPORT_UNWINDLIB_NONE_FLAG)
+ set(CMAKE_REQUIRED_FLAGS "${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()
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