Build fails without -latomic on Clang 8.0

[mqudsi]

master doesn't compile under Clang 8.0 (Ubuntu 18.04.1 LTS) due to missing __atomic_* symbols such as __atomic_load and __atomic_store, which are provided by the GCC libatomic.

[6/7] Linking CXX executable fish                                                                                                                                FAILED: fish
: && /usr/local/bin/sc++  -march=native -msse4a -mavx2 -mfma -msha -fdiagnostics-color=always -O2 -g  -rdynamic CMakeFiles/fish.dir/src/fish.cpp.o  -o fish  libfishlib.a -lcurses -pthread -ldl -lpcre2-32 && :
/usr/local/bin/ld: libfishlib.a(wutil.cpp.o): in function `safe_strerror(int)':
/mnt/d/rand/fish/build/../src/wutil.cpp:334: warning: `sys_errlist' is deprecated; use `strerror' or `strerror_r' instead
/usr/local/bin/ld: /mnt/d/rand/fish/build/../src/wutil.cpp:334: warning: `sys_nerr' is deprecated; use `strerror' or `strerror_r' instead
/usr/local/bin/ld: libfishlib.a(common.cpp.o): in function `std::atomic<winsize>::load(std::memory_order) const':
/usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/atomic:250: undefined reference to `__atomic_load'
/usr/local/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/atomic:250: undefined reference to `__atomic_load'
/usr/local/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/atomic:250: undefined reference to `__atomic_load'
/usr/local/bin/ld: libfishlib.a(common.cpp.o): in function `std::atomic<winsize>::store(winsize, std::memory_order)':
/usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/atomic:239: undefined reference to `__atomic_store'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

The following hack fixes the build:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0179915f..192a12f3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -143,7 +143,7 @@ ADD_LIBRARY(fishlib STATIC ${FISH_SRCS})
 TARGET_SOURCES(fishlib PRIVATE ${FISH_HEADERS})
 TARGET_LINK_LIBRARIES(fishlib
   ${CURSES_LIBRARY} ${CURSES_EXTRA_LIBRARY} Threads::Threads ${CMAKE_DL_LIBS}
-  ${PCRE2_LIB} ${Intl_LIBRARIES})
+  ${PCRE2_LIB} ${Intl_LIBRARIES} "atomic")
 
 # Define fish.
 ADD_EXECUTABLE(fish src/fish.cpp)

I'm not sure what the correct way of testing for -latomic and using it is with CMake.

Build logs:
CMakeError.log
CMakeOutput.log

[zanchey]

Is sc++ some custom compiler?

The right thing to do is to make a CheckAtomic function, similar to https://github.com/llvm-mirror/llvm/blob/master/cmake/modules/CheckAtomic.cmake

[mqudsi]

No, it's just exec ccache c++ to speed up compilation, where c++ is pointing at clang++-8.

[zanchey]

This is still an issue as of 8bf9f52, though only on armv7l:

/usr/bin/ld: libfishlib.a(history.cpp.o): in function `history_t::add_pending_with_file_detection(std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> > const&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> > const&)':
/usr/include/c++/8/bits/atomic_base.h:514: undefined reference to `__atomic_fetch_add_8'
/usr/bin/ld: libfishlib.a(proc.cpp.o): in function `internal_proc_t::internal_proc_t()':
/usr/include/c++/8/bits/atomic_base.h:296: undefined reference to `__atomic_fetch_add_8'
/usr/bin/ld: libfishlib.a(reader.cpp.o): in function `reader_run_count()':
/usr/include/c++/8/bits/atomic_base.h:396: undefined reference to `__atomic_load_8'
/usr/bin/ld: libfishlib.a(reader.cpp.o): in function `reader_read(parser_t&, int, io_chain_t const&)':
/usr/include/c++/8/bits/atomic_base.h:514: undefined reference to `__atomic_fetch_add_8'
collect2: error: ld returned 1 exit status

(gold's error messages are much less useful than GNU ld)

[mqudsi]

I can confirm that it's not an issue on ARMv8; I spun up an armv8 instance on AWS and it's not an issue there (mainly because I missed the v7 part of your post):

root@freebsd:/usr/home/ec2-user/fish-shell # uname -a
FreeBSD freebsd 12.1-RELEASE FreeBSD 12.1-RELEASE r354233 GENERIC  arm64
root@freebsd:/usr/home/ec2-user/fish-shell # ldd build/fish
build/fish:
        libncurses.so.8 => /lib/libncurses.so.8 (0x403c1000)
        libintl.so.8 => /usr/local/lib/libintl.so.8 (0x40432000)
        libc++.so.1 => /usr/lib/libc++.so.1 (0x40473000)
        libcxxrt.so.1 => /lib/libcxxrt.so.1 (0x40566000)
        libm.so.5 => /lib/libm.so.5 (0x405ab000)
        libthr.so.3 => /lib/libthr.so.3 (0x4061c000)
        libc.so.7 => /lib/libc.so.7 (0x40678000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x40a3f000)
root@freebsd:/usr/home/ec2-user/fish-shell #

What's your armv7 test platform, @zanchey?

[zanchey]

Linux titan 4.19.75-v7l+ #1270 SMP Tue Sep 24 18:51:41 BST 2019 armv7l GNU/Linux (Raspbian GNU/Linux 10)

Probably this is a 32-bit issue.

[zanchey]

The test for this still isn't right - libatomic is not available on RHEL 6/7, but the test fails there.

[zanchey]

Looks like this is finally working in 45633f4