[clang] 3b78dfa - [libc][libcxx] Support for building libc++ against LLVM libc (#99287)
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Thu Jul 18 22:17:46 PDT 2024
Author: Petr Hosek
Date: 2024-07-18T22:17:42-07:00
New Revision: 3b78dfa10c4b77581cc29c4510aefe919ae660ba
URL: https://github.com/llvm/llvm-project/commit/3b78dfa10c4b77581cc29c4510aefe919ae660ba
DIFF: https://github.com/llvm/llvm-project/commit/3b78dfa10c4b77581cc29c4510aefe919ae660ba.diff
LOG: [libc][libcxx] Support for building libc++ against LLVM libc (#99287)
Provide an option to build libc++ against LLVM libc and set the CMake
compile and link options appropriately when the option is enabled.
Added:
libcxx/cmake/Modules/HandleLibC.cmake
Modified:
clang/cmake/caches/Fuchsia-stage2.cmake
libcxx/CMakeLists.txt
libcxx/cmake/config-ix.cmake
libcxx/include/CMakeLists.txt
libcxx/src/CMakeLists.txt
Removed:
################################################################################
diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
index 73ebd36c28496..0218f0b21eb28 100644
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -339,6 +339,7 @@ foreach(target armv6m-unknown-eabi;armv7m-unknown-eabi;armv8m.main-unknown-eabi)
set(RUNTIMES_${target}_LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_STATIC ON CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")
+ set(RUNTIMES_${target}_LIBCXX_LIBC "llvm-libc" CACHE STRING "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_LOCALIZATION OFF CACHE BOOL "")
@@ -389,6 +390,7 @@ foreach(target riscv32-unknown-elf)
set(RUNTIMES_${target}_LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_STATIC ON CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")
+ set(RUNTIMES_${target}_LIBCXX_LIBC "llvm-libc" CACHE STRING "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_LOCALIZATION OFF CACHE BOOL "")
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 155f81a74a974..332816b15260a 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -212,6 +212,14 @@ set(LIBCXX_ABI_DEFINES "" CACHE STRING "A semicolon separated list of ABI macros
set(LIBCXX_EXTRA_SITE_DEFINES "" CACHE STRING "Extra defines to add into __config_site")
option(LIBCXX_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)
+# C Library options -----------------------------------------------------------
+
+set(LIBCXX_SUPPORTED_C_LIBRARIES system llvm-libc)
+set(LIBCXX_LIBC "system" CACHE STRING "Specify C library to use. Supported values are ${LIBCXX_SUPPORTED_C_LIBRARIES}.")
+if (NOT "${LIBCXX_LIBC}" IN_LIST LIBCXX_SUPPORTED_C_LIBRARIES)
+ message(FATAL_ERROR "Unsupported C library: '${LIBCXX_CXX_ABI}'. Supported values are ${LIBCXX_SUPPORTED_C_LIBRARIES}.")
+endif()
+
# ABI Library options ---------------------------------------------------------
if (MSVC)
set(LIBCXX_DEFAULT_ABI_LIBRARY "vcruntime")
@@ -495,6 +503,7 @@ endif()
# Setup Compiler Flags
#===============================================================================
+include(HandleLibC) # Setup the C library flags
include(HandleLibCXXABI) # Setup the ABI library flags
# FIXME(EricWF): See the FIXME on LIBCXX_ENABLE_PEDANTIC.
diff --git a/libcxx/cmake/Modules/HandleLibC.cmake b/libcxx/cmake/Modules/HandleLibC.cmake
new file mode 100644
index 0000000000000..1b0564ae6fcc6
--- /dev/null
+++ b/libcxx/cmake/Modules/HandleLibC.cmake
@@ -0,0 +1,39 @@
+#===============================================================================
+# Define targets for linking against the selected C library
+#
+# After including this file, the following targets are defined:
+# - libcxx-libc-headers: An interface target that allows getting access to the
+# headers of the selected C library.
+# - libcxx-libc-shared: A target representing the selected shared C library.
+# - libcxx-libc-static: A target representing the selected static C library.
+#===============================================================================
+
+# Link against a system-provided libc
+if (LIBCXX_LIBC STREQUAL "system")
+ add_library(libcxx-libc-headers INTERFACE)
+
+ add_library(libcxx-libc-static INTERFACE)
+ add_library(libcxx-libc-shared INTERFACE)
+
+# Link against the in-tree LLVM libc
+elseif (LIBCXX_LIBC STREQUAL "llvm-libc")
+ add_library(libcxx-libc-headers INTERFACE)
+ target_link_libraries(libcxx-libc-headers INTERFACE libc-headers)
+ if(CXX_SUPPORTS_NOSTDLIBINC_FLAG)
+ target_compile_options(libcxx-libc-headers INTERFACE "-nostdlibinc")
+ endif()
+
+ add_library(libcxx-libc-static INTERFACE)
+ if (TARGET libc)
+ target_link_libraries(libcxx-libc-static INTERFACE libc)
+ endif()
+ if (TARGET libm)
+ target_link_libraries(libcxx-libc-static INTERFACE libm)
+ endif()
+ if (CXX_SUPPORTS_NOLIBC_FLAG)
+ target_link_options(libcxx-libc-static INTERFACE "-nolibc")
+ endif()
+
+ # TODO: There's no support for building LLVM libc as a shared library yet.
+ add_library(libcxx-libc-shared INTERFACE)
+endif()
diff --git a/libcxx/cmake/config-ix.cmake b/libcxx/cmake/config-ix.cmake
index 7406fba482e69..998819604de28 100644
--- a/libcxx/cmake/config-ix.cmake
+++ b/libcxx/cmake/config-ix.cmake
@@ -27,6 +27,9 @@ if (NOT LIBCXX_USE_COMPILER_RT)
endif()
endif()
+check_cxx_compiler_flag(-nostdlibinc CXX_SUPPORTS_NOSTDLIBINC_FLAG)
+check_cxx_compiler_flag(-nolibc CXX_SUPPORTS_NOLIBC_FLAG)
+
# libc++ is using -nostdlib++ at the link step when available,
# otherwise -nodefaultlibs is used. We want all our checks to also
# use one of these options, otherwise we may end up with an inconsistency between
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 4b036ec639507..fa6736dc11e66 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -1043,7 +1043,7 @@ list(APPEND _all_includes "${LIBCXX_GENERATED_INCLUDE_DIR}/libcxx.imp")
add_custom_target(generate-cxx-headers ALL DEPENDS ${_all_includes})
add_library(cxx-headers INTERFACE)
-target_link_libraries(cxx-headers INTERFACE libcxx-abi-headers)
+target_link_libraries(cxx-headers INTERFACE libcxx-libc-headers libcxx-abi-headers)
add_dependencies(cxx-headers generate-cxx-headers)
# It's important that the arch directory be included first so that its header files
# which interpose on the default include dir be included instead of the default ones.
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 0ae58a10c879c..0dfc9647558d4 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -199,7 +199,7 @@ split_list(LIBCXX_LINK_FLAGS)
if (LIBCXX_ENABLE_SHARED)
add_library(cxx_shared SHARED ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
target_include_directories(cxx_shared PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
- target_link_libraries(cxx_shared PUBLIC cxx-headers
+ target_link_libraries(cxx_shared PUBLIC cxx-headers libcxx-libc-shared
PRIVATE ${LIBCXX_LIBRARIES})
set_target_properties(cxx_shared
PROPERTIES
@@ -292,7 +292,7 @@ set(CMAKE_STATIC_LIBRARY_PREFIX "lib")
if (LIBCXX_ENABLE_STATIC)
add_library(cxx_static STATIC ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
target_include_directories(cxx_static PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
- target_link_libraries(cxx_static PUBLIC cxx-headers
+ target_link_libraries(cxx_static PUBLIC cxx-headers libcxx-libc-static
PRIVATE ${LIBCXX_LIBRARIES}
PRIVATE libcxx-abi-static)
set_target_properties(cxx_static
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