How to build Boost with Clang/libc++ and NOT link against libstdc++?
Hi guys, I am struggling with building the Boost (1.58.0) libraries with Clang (3.8) and libc++ (on Ubuntu 16.04). I am able to build the Boost libraries using Clang and flags "-std=c++14 -stdlib=libc++", however, I noticed that several libraries are still linked against GCC's standard-library "libstdc++". I then tried adding the flag "-lc++abi" (later I tried "-Wl,-lc++abi") to Boost.Build options "cxxflags" and "linkflags" to explicitly link against "libc++abi". With no luck. Several boost-libraries are still linked against "libstdc++". Does anyone know how and why this link-dependency gets added and how to get rid of them? Does it come in through some other link-dependencies? At least none of them seem to link to "libstdc++"? The Boost shared-libraries that link to "libstdc++" are: libboost_chrono-clang38-mt-1_58_0.so.1.58.0 libboost_context-clang38-mt-1_58_0.so.1.58.0 libboost_coroutine-clang38-mt-1_58_0.so.1.58.0 libboost_date_time-clang38-mt-1_58_0.so.1.58.0 libboost_filesystem-clang38-mt-1_58_0.so.1.58.0 libboost_graph-clang38-mt-1_58_1.so.0.58.0 libboost_iostreams-clang38-mt-1_58_0.so.1.58.0 libboost_locale-clang38-mt-1_58_0.so.1.58.0 libboost_log-clang38-mt-1_58_0.so.1.58.0 libboost_log_setup-clang38-mt-1_58_0.so.1.58.0 libboost_math_tr1-clang38-mt-1_58_0.so.1.58.0 libboost_math_tr1f-clang38-mt-1_58_0.so.1.58.0 libboost_math_tr1l-clang38-mt-1_58_0.so.1.58.0 libboost_program_options-clang38-mt-1_58_0.so.1.58.0 libboost_python-clang38-mt-1_58_0.so.1.58.0 libboost_random-clang38-mt-1_58_0.so.1.58.0 libboost_regex-clang38-mt-1_58_0.so.1.58.0 libboost_signals-clang38-mt-1_58_0.so.1.58.0 libboost_thread-clang38-mt-1_58_0.so.1.58.0 libboost_timer-clang38-mt-1_58_0.so.1.58.0 libboost_unit_test_framework-clang38-mt-1_58_0.so.1.58.0 libboost_wave-clang38-mt-1_58_0.so.1.58.0 The once that are fine and do not link against "libstdc++" are: libboost_atomic-clang38-mt-1_58_0.so.1.58.0 libboost_container-clang38-mt-1_58_0.so.1.58.0 libboost_math_c99-clang38-mt-1_58_0.so.1.58.0 libboost_math_c99f-clang38-mt-1_58_0.so.1.58.0 libboost_math_c99l-clang38-mt-1_58_0.so.1.58.0 libboost_serialization-clang38-mt-1_58_0.so.1.58.0 libboost_system-clang38-mt-1_58_0.so.1.58.0 libboost_wserialization-clang38-mt-1_58_0.so.1.58.0 Interestingly, all libraries are also linked against "libc++abi" except for: libboost_atomic-clang38-mt-1_58_0.so.1.58.0 libboost_container-clang38-mt-1_58_0.so.1.5 For completeness, my build-command is this: cd /home/jenkins/workspace/Pipeline_Boost/sources/boost_1_58_0 LINK_LIBCXXABI="-Wl,-lc++abi" COMMON_COMPILER_FLAGS="-m64 -fpic -fdiagnostics-color=always -O3" CFLAGS="$COMMON_COMPILER_FLAGS" CXXFLAGS="$COMMON_COMPILER_FLAGS -std=c++14 -stdlib=libc++ -isystem/usr/include/libcxxabi $LINK_LIBCXXABI" CC=/usr/bin/clang-3.8 CXX=/usr/bin/clang++-3.8 /home/jenkins/workspace/Pipeline_Boost@3/clang38/build/boost-build/b2 -j1 -q \ --build-dir=/home/jenkins/workspace/Pipeline_Boost@3/clang38/build/boost \ --build-type=minimal --layout=versioned address-model=64 install \ --prefix=/home/jenkins/workspace/Pipeline_Boost@3/clang38/installed/opt/BENOCS/clang38 \ --libdir=/home/jenkins/workspace/Pipeline_Boost@3/clang38/installed/opt/BENOCS/clang38/lib/x86_64-linux-gnu \ dll-path==/opt/BENOCS/clang38/lib/x86_64-linux-gnu \ toolset=clang-3.8 \ cflags="$CFLAGS" CXXFLAGS="$CXXFLAGS" \ linkflags="-Wl,--as-needed $LINK_LIBCXXABI" For the environment-variable LINK_LIBCXXABI I tried "-lc++abi" as well and also tried providing it only in the cxxflags or the linkflags or both (as above). I would be happy, if anyone could explain that behavior or could even provide a workaround/fix for me, so that "libstdc++" is no longer linked. Thanks, Deniz PS: BTW, does anyone know if it is correct, that shared libraries (in general) that are linked against "libc++abi" do always also link to "libgcc_s"? (What is it for?) -- BENOCS GmbH Dipl.-Inform. Deniz Bahadir Winterfeldtstr. 21 10781 Berlin Germany Phone: +49 - 30 / 577 0004-22 Email: deniz.bahadir@benocs.com www.benocs.com Board of Management: Michael Wolz, Dr.-Ing. Oliver Holschke, Dr.-Ing. Ingmar Poese Commercial Register: Amtsgericht Bonn HRB 19378
Hi Deniz, Am Freitag, 20. Januar 2017, 10:13:56 CET schrieb Deniz Bahadir:
Hi guys, I am able to build the Boost libraries using Clang and flags "-std=c++14 -stdlib=libc++", however, I noticed that several libraries are still linked against GCC's standard-library "libstdc++".
This works for me for quite a while. Please make sure you rebuild all libraries. Hint: b2 does not cache compiler flags. Add "-a" to your command line to force a full rebuild.
Does anyone know how and why this link-dependency gets added and how to get rid of them? Does it come in through some other link-dependencies? At least none of them seem to link to "libstdc++"?
Most probably a not clean rebuild.
dll-path==/opt/BENOCS/clang38/lib/x86_64-linux-gnu \ toolset=clang-3.8 \
The toolset "clang-3.8" is configured where and how?
cflags="$CFLAGS" CXXFLAGS="$CXXFLAGS" \
cxxflags="$CXXFLAGS"
linkflags="-Wl,--as-needed $LINK_LIBCXXABI"
I'd put the extra flags into user-/project-/site-config.jam.
For the environment-variable LINK_LIBCXXABI I tried "-lc++abi" as well and also tried providing it only in the cxxflags or the linkflags or both (as above).
linkflags should contain "-stdlib=libc++", too
I would be happy, if anyone could explain that behavior or could even provide a workaround/fix for me, so that "libstdc++" is no longer linked.
from my user-config.jam: # Clang trunk using clang : # version : # compiler $(HOME)/local/bin/clang++ : # options <cxxflags>-stdlib=libc++ <cxxflags>-I$(HOME)/local/include/c++/v1 <linkflags>-stdlib=libc++ <linkflags>-L$(HOME)/local/lib ; with custom clang trunk installed to $(HOME)/local
PS: BTW, does anyone know if it is correct, that shared libraries (in general) that are linked against "libc++abi" do always also link to "libgcc_s"? (What is it for?)
The basic compiler runtime AFAIK. Might be replaced by clang's compiler-rt, I guess. But that is off-topic Yours, Jürgen -- * Dipl.-Math. Jürgen Hunold ! * voice: ++49 4257 300 ! Fährstraße 1 * fax : ++49 4257 300 ! 31609 Balge/Sebbenhausen * jhunold@gmx.eu ! Germany
Hi Jürgen, thanks for your answer. Am 20.01.2017 um 12:40 schrieb Jürgen Hunold:
Hi Deniz,
Am Freitag, 20. Januar 2017, 10:13:56 CET schrieb Deniz Bahadir:
Hi guys, I am able to build the Boost libraries using Clang and flags "-std=c++14 -stdlib=libc++", however, I noticed that several libraries are still linked against GCC's standard-library "libstdc++".
This works for me for quite a while. Please make sure you rebuild all libraries. Hint: b2 does not cache compiler flags. Add "-a" to your command line to force a full rebuild.
[...]
Most probably a not clean rebuild.
I built the libraries using our build-server which made sure to use an entirely new build- and source-directory. So that should not be the problem in my case.
dll-path==/opt/BENOCS/clang38/lib/x86_64-linux-gnu \ toolset=clang-3.8 \
The toolset "clang-3.8" is configured where and how?
I cannot really tell. At least it works. It uses the correct clang-executable.
cflags="$CFLAGS" CXXFLAGS="$CXXFLAGS" \
cxxflags="$CXXFLAGS"
Yes, you are right. However, that error just went in when writing this email. The build-server used the correct command.
linkflags="-Wl,--as-needed $LINK_LIBCXXABI"
I'd put the extra flags into user-/project-/site-config.jam.
I am not so fond of using these. I always get confused how they work, where they have to be located and to what project it applies. Especially, as our build-server builds boost with several compilers with (possibly) different settings.
For the environment-variable LINK_LIBCXXABI I tried "-lc++abi" as well and also tried providing it only in the cxxflags or the linkflags or both (as above).
linkflags should contain "-stdlib=libc++", too
I think, that did the trick. :-) It no longer links against "libstdc++".
[...]
PS: BTW, does anyone know if it is correct, that shared libraries (in general) that are linked against "libc++abi" do always also link to "libgcc_s"? (What is it for?)
The basic compiler runtime AFAIK. Might be replaced by clang's compiler-rt, I guess. But that is off-topic
Thanks for this additional insight.
Yours,
Jürgen
Thanks a lot, Deniz -- BENOCS GmbH Dipl.-Inform. Deniz Bahadir Winterfeldtstr. 21 10781 Berlin Germany Phone: +49 - 30 / 577 0004-22 Email: deniz.bahadir@benocs.com www.benocs.com Board of Management: Michael Wolz, Dr.-Ing. Oliver Holschke, Dr.-Ing. Ingmar Poese Commercial Register: Amtsgericht Bonn HRB 19378
participants (4)
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Deniz Bahadir -
Jürgen Hunold