[libc-commits] [clang] [libc] [libcxx] [libc][libcxx] Support for building libc++ against LLVM libc (PR #99287)
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Wed Jul 17 00:53:32 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Petr Hosek (petrhosek)
<details>
<summary>Changes</summary>
Provide an option to build libc++ against LLVM libc and set the CMake compile and link options appropriately when the option is enabled.
---
Full diff: https://github.com/llvm/llvm-project/pull/99287.diff
7 Files Affected:
- (modified) clang/cmake/caches/Fuchsia-stage2.cmake (+2)
- (modified) libc/cmake/modules/CheckCompilerFeatures.cmake (+3)
- (modified) libc/include/CMakeLists.txt (+3)
- (modified) libc/lib/CMakeLists.txt (+4-1)
- (modified) libcxx/CMakeLists.txt (+1)
- (modified) libcxx/include/CMakeLists.txt (+3)
- (modified) libcxx/src/CMakeLists.txt (+10)
``````````diff
diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
index b4561e6c87ba5..dc9b596b4ba8f 100644
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -338,6 +338,7 @@ foreach(target armv6m-unknown-eabi;armv7m-unknown-eabi;armv8m.main-unknown-eabi)
set(RUNTIMES_${target}_LIBCXX_CXX_ABI none CACHE STRING "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_STATIC ON CACHE BOOL "")
+ set(RUNTIMES_${target}_LIBCXX_USE_LLVM_LIBC ON CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_LOCALIZATION OFF CACHE BOOL "")
@@ -388,6 +389,7 @@ foreach(target riscv32-unknown-elf)
set(RUNTIMES_${target}_LIBCXX_CXX_ABI none CACHE STRING "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
set(RUNTIMES_${target}_LIBCXX_ENABLE_STATIC ON CACHE BOOL "")
+ set(RUNTIMES_${target}_LIBCXX_USE_LLVM_LIBC ON CACHE BOOL "")
set(RUNTIMES_${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/libc/cmake/modules/CheckCompilerFeatures.cmake b/libc/cmake/modules/CheckCompilerFeatures.cmake
index a6d793d495c45..d64d9de97af3c 100644
--- a/libc/cmake/modules/CheckCompilerFeatures.cmake
+++ b/libc/cmake/modules/CheckCompilerFeatures.cmake
@@ -102,3 +102,6 @@ check_cxx_compiler_flag("-nostdlib++" LIBC_CC_SUPPORTS_NOSTDLIBPP)
# clang-3.0+
check_cxx_compiler_flag("-nostdlibinc" LIBC_CC_SUPPORTS_NOSTDLIBINC)
+
+# clang-3.0+
+check_cxx_compiler_flag("-nolibc" LIBC_CC_SUPPORTS_NOLIBC)
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 2cf7206f3a625..d521e205df8c3 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -664,6 +664,9 @@ get_all_install_header_targets(all_install_header_targets ${TARGET_PUBLIC_HEADER
add_library(libc-headers INTERFACE)
add_dependencies(libc-headers ${all_install_header_targets})
target_include_directories(libc-headers SYSTEM INTERFACE ${LIBC_INCLUDE_DIR})
+if(LIBC_CC_SUPPORTS_NOSTDLIBINC)
+ target_compile_options(libc-headers INTERFACE "-nostdlibinc")
+endif()
foreach(target IN LISTS all_install_header_targets)
get_target_property(header_file ${target} HEADER_FILE_PATH)
diff --git a/libc/lib/CMakeLists.txt b/libc/lib/CMakeLists.txt
index 37acf3950b460..7e18f35e7d60e 100644
--- a/libc/lib/CMakeLists.txt
+++ b/libc/lib/CMakeLists.txt
@@ -30,7 +30,10 @@ foreach(archive IN ZIP_LISTS
ARCHIVE_OUTPUT_NAME ${archive_0}
)
if(LLVM_LIBC_FULL_BUILD)
- target_link_libraries(${archive_1} PUBLIC libc-headers)
+ target_link_libraries(${archive_1} INTERFACE libc-headers)
+ if(LIBC_CC_SUPPORTS_NOLIBC)
+ target_link_options(${archive_1} INTERFACE "-nolibc")
+ endif()
if(TARGET libc-startup)
add_dependencies(${archive_1} libc-startup)
endif()
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 190a97db9462f..5a568e95b239e 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -293,6 +293,7 @@ option(LIBCXX_ENABLE_THREADS "Build libc++ with support for threads." ON)
option(LIBCXX_ENABLE_MONOTONIC_CLOCK
"Build libc++ with support for a monotonic clock.
This option may only be set to OFF when LIBCXX_ENABLE_THREADS=OFF." ON)
+option(LIBCXX_USE_LLVM_LIBC "Build libc++ against LLVM libc." OFF)
option(LIBCXX_HAS_MUSL_LIBC "Build libc++ with support for the Musl C library" OFF)
option(LIBCXX_HAS_PTHREAD_API "Ignore auto-detection and force use of pthread API" OFF)
option(LIBCXX_HAS_WIN32_THREAD_API "Ignore auto-detection and force use of win32 thread API" OFF)
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index cd64fe91449c2..31a819932d521 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -1043,6 +1043,9 @@ add_custom_target(generate-cxx-headers ALL DEPENDS ${_all_includes})
add_library(cxx-headers INTERFACE)
target_link_libraries(cxx-headers INTERFACE libcxx-abi-headers)
+if (LIBCXX_USE_LLVM_LIBC)
+ target_link_libraries(cxx-headers INTERFACE libc-headers)
+endif()
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..536a5a16ad7e1 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -229,6 +229,11 @@ if (LIBCXX_ENABLE_SHARED)
target_link_libraries(cxx_shared PUBLIC libcxx-abi-shared)
endif()
+ # Link against LLVM libc.
+ if (LIBCXX_USE_LLVM_LIBC)
+ target_link_libraries(cxx_shared PUBLIC libc libm)
+ endif()
+
# Maybe re-export symbols from libc++abi
# In particular, we don't re-export the symbols if libc++abi is merged statically
# into libc++ because in that case there's no dylib to re-export from.
@@ -324,6 +329,11 @@ if (LIBCXX_ENABLE_STATIC)
if (LIBCXX_STATICALLY_LINK_ABI_IN_STATIC_LIBRARY)
target_link_libraries(cxx_static PRIVATE libcxx-abi-static-objects)
endif()
+
+ # Link against LLVM libc.
+ if (LIBCXX_USE_LLVM_LIBC)
+ target_link_libraries(cxx_static PUBLIC libc libm)
+ endif()
endif()
# Add a meta-target for both libraries.
``````````
</details>
https://github.com/llvm/llvm-project/pull/99287
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