[libcxx-commits] [libcxxabi] 5f9be2c - [SystemZ][ZOS] Prefer -nostdlib++ as opposed to -nodefaultlibs when building c++ libraries
Zbigniew Sarbinowski via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Feb 16 10:43:02 PST 2021
Author: Zbigniew Sarbinowski
Date: 2021-02-16T18:42:14Z
New Revision: 5f9be2c3e37c0428ba56876dd84af04b8d9d8915
URL: https://github.com/llvm/llvm-project/commit/5f9be2c3e37c0428ba56876dd84af04b8d9d8915
DIFF: https://github.com/llvm/llvm-project/commit/5f9be2c3e37c0428ba56876dd84af04b8d9d8915.diff
LOG: [SystemZ][ZOS] Prefer -nostdlib++ as opposed to -nodefaultlibs when building c++ libraries
Let's use -nostdlib++ rather than -nodefaultlibs when building libc++/libc++abi/libunwind libraries. The default is -nostdlib++ if supported by a build compiler like it is the case with clang, otherwise -nodefaultlibs is used as before.
This change is needed to avoid additional changes at the link step and not to increase the maintenance costs. If clang with -nodefaultlibs is used all the libraries which are removed but required would have to be manually added in. This set of libraries are unique and will send out.
The propose change will allow to make the link step simple for other platforms as well.
Reviewed By: #libc, #libc_abi, ldionne
Differential Revision: https://reviews.llvm.org/D95875
Added:
Modified:
libcxx/CMakeLists.txt
libcxx/cmake/config-ix.cmake
libcxxabi/cmake/config-ix.cmake
libcxxabi/src/CMakeLists.txt
libunwind/cmake/config-ix.cmake
libunwind/src/CMakeLists.txt
Removed:
################################################################################
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 43f7cbbb31ab..1144f4568d84 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -725,9 +725,19 @@ endif()
# Link system libraries =======================================================
function(cxx_link_system_libraries target)
- target_add_link_flags_if_supported(${target} PRIVATE "-nodefaultlibs")
- target_add_compile_flags_if_supported(${target} PRIVATE "/Zl")
- target_add_link_flags_if_supported(${target} PRIVATE "/nodefaultlib")
+
+# In order to remove just libc++ from the link step
+# we need to use -nostdlib++ whenever it is supported.
+# Unfortunately this cannot be used universally because for example g++ supports
+# only -nodefaultlibs in which case all libraries will be removed and
+# all libraries but c++ have to be added in manually.
+ if (LIBCXX_SUPPORTS_NOSTDLIBXX_FLAG)
+ target_add_link_flags_if_supported(${target} PRIVATE "-nostdlib++")
+ else()
+ target_add_link_flags_if_supported(${target} PRIVATE "-nodefaultlibs")
+ target_add_compile_flags_if_supported(${target} PRIVATE "/Zl")
+ target_add_link_flags_if_supported(${target} PRIVATE "/nodefaultlib")
+ endif()
if (LIBCXX_HAS_SYSTEM_LIB)
target_link_libraries(${target} PRIVATE System)
diff --git a/libcxx/cmake/config-ix.cmake b/libcxx/cmake/config-ix.cmake
index 894f637f814f..a2f1ff9f1a3b 100644
--- a/libcxx/cmake/config-ix.cmake
+++ b/libcxx/cmake/config-ix.cmake
@@ -24,16 +24,26 @@ if (NOT LIBCXX_USE_COMPILER_RT)
endif()
endif()
-# libc++ is built with -nodefaultlibs, so we want all our checks to also
-# use this option, otherwise we may end up with an inconsistency between
+# 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
# the flags we think we require during configuration (if the checks are
-# performed without -nodefaultlibs) and the flags that are actually
-# required during compilation (which has the -nodefaultlibs). libc is
+# performed without one of those options) and the flags that are actually
+# required during compilation (which has the -nostdlib++ or -nodefaultlibs). libc is
# required for the link to go through. We remove sanitizers from the
# configuration checks to avoid spurious link errors.
-check_c_compiler_flag(-nodefaultlibs LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
-if (LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
- set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
+
+check_c_compiler_flag(-nostdlib++ LIBCXX_SUPPORTS_NOSTDLIBXX_FLAG)
+if (LIBCXX_SUPPORTS_NOSTDLIBXX_FLAG)
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
+else()
+ check_c_compiler_flag(-nodefaultlibs LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
+ if (LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
+ endif()
+endif()
+
+if (LIBCXX_SUPPORTS_NOSTDLIBXX_FLAG OR LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBCXX_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
diff --git a/libcxxabi/cmake/config-ix.cmake b/libcxxabi/cmake/config-ix.cmake
index 15b52083fee2..7f1cecbcd254 100644
--- a/libcxxabi/cmake/config-ix.cmake
+++ b/libcxxabi/cmake/config-ix.cmake
@@ -14,16 +14,26 @@ if (NOT LIBCXXABI_USE_COMPILER_RT)
endif ()
endif ()
-# libc++abi is built with -nodefaultlibs, so we want all our checks to also
-# use this option, otherwise we may end up with an inconsistency between
+# libc++abi is using -nostdlib++ at the link step when available,
+# otherwise -nodefaultlibs is used. We want all our checks to also
+# use one of these options, otherwise we may end up with an inconsistency between
# the flags we think we require during configuration (if the checks are
# performed without -nodefaultlibs) and the flags that are actually
# required during compilation (which has the -nodefaultlibs). libc is
# required for the link to go through. We remove sanitizers from the
# configuration checks to avoid spurious link errors.
-check_c_compiler_flag(-nodefaultlibs LIBCXXABI_HAS_NODEFAULTLIBS_FLAG)
-if (LIBCXXABI_HAS_NODEFAULTLIBS_FLAG)
- set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
+
+check_c_compiler_flag(-nostdlib++ LIBCXXABI_SUPPORTS_NOSTDLIBXX_FLAG)
+if (LIBCXXABI_SUPPORTS_NOSTDLIBXX_FLAG)
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
+else()
+ check_c_compiler_flag(-nodefaultlibs LIBCXXABI_SUPPORTS_NODEFAULTLIBS_FLAG)
+ if (LIBCXXABI_SUPPORTS_NODEFAULTLIBS_FLAG)
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
+ endif()
+endif()
+
+if (LIBCXXABI_SUPPORTS_NOSTDLIBXX_FLAG OR LIBCXXABI_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBCXXABI_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
index a8e12aa36e64..9003f79bbed1 100644
--- a/libcxxabi/src/CMakeLists.txt
+++ b/libcxxabi/src/CMakeLists.txt
@@ -109,7 +109,11 @@ if (NOT LIBCXXABI_USE_COMPILER_RT)
endif ()
# Setup flags.
-add_link_flags_if_supported(-nodefaultlibs)
+if (LIBCXXABI_SUPPORTS_NOSTDLIBXX_FLAG)
+ add_link_flags_if_supported(-nostdlib++)
+else()
+ add_link_flags_if_supported(-nodefaultlibs)
+endif()
if ( APPLE )
if (LLVM_USE_SANITIZER)
diff --git a/libunwind/cmake/config-ix.cmake b/libunwind/cmake/config-ix.cmake
index 3e42818882b3..4ca6bdd8e95d 100644
--- a/libunwind/cmake/config-ix.cmake
+++ b/libunwind/cmake/config-ix.cmake
@@ -16,16 +16,26 @@ if (NOT LIBUNWIND_USE_COMPILER_RT)
endif ()
endif()
-# libunwind is built with -nodefaultlibs, so we want all our checks to also
-# use this option, otherwise we may end up with an inconsistency between
+# libunwind 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
# the flags we think we require during configuration (if the checks are
-# performed without -nodefaultlibs) and the flags that are actually
-# required during compilation (which has the -nodefaultlibs). libc is
+# performed without one of those options) and the flags that are actually
+# required during compilation (which has the -nostdlib++ or -nodefaultlibs). libc is
# required for the link to go through. We remove sanitizers from the
# configuration checks to avoid spurious link errors.
-check_c_compiler_flag(-nodefaultlibs LIBUNWIND_HAS_NODEFAULTLIBS_FLAG)
-if (LIBUNWIND_HAS_NODEFAULTLIBS_FLAG)
- set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
+
+check_c_compiler_flag(-nostdlib++ LIBUNWIND_SUPPORTS_NOSTDLIBXX_FLAG)
+if (LIBUNWIND_SUPPORTS_NOSTDLIBXX_FLAG)
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
+else()
+ check_c_compiler_flag(-nodefaultlibs LIBUNWIND_SUPPORTS_NODEFAULTLIBS_FLAG)
+ if (LIBUNWIND_SUPPORTS_NODEFAULTLIBS_FLAG)
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
+ endif()
+endif()
+
+if (LIBUNWIND_SUPPORTS_NOSTDLIBXX_FLAG OR LIBUNWIND_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBUNWIND_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
diff --git a/libunwind/src/CMakeLists.txt b/libunwind/src/CMakeLists.txt
index dc2c5e0087e9..a7045d2c317f 100644
--- a/libunwind/src/CMakeLists.txt
+++ b/libunwind/src/CMakeLists.txt
@@ -80,7 +80,11 @@ if (LIBUNWIND_ENABLE_THREADS)
endif()
# Setup flags.
-add_link_flags_if_supported(-nodefaultlibs)
+if (LIBUNWIND_SUPPORTS_NOSTDLIBXX_FLAG)
+ add_link_flags_if_supported(-nostdlib++)
+else()
+ add_link_flags_if_supported(-nodefaultlibs)
+endif()
# MINGW_LIBRARIES is defined in config-ix.cmake
add_library_flags_if(MINGW "${MINGW_LIBRARIES}")
More information about the libcxx-commits
mailing list