1.0.1 fails to build on FreeBSD

[jbeich]

Regressed by 7438638. Found downstream. On FreeBSD libatomic is not present because the default toolchain is LLVM-based (Clang, LLD, libc++, compiler-rt).

$ cmake -DBUILD_TESTING=off -G Ninja -B /tmp/highway_build
-- The C compiler identification is Clang 14.0.5
-- The CXX compiler identification is Clang 14.0.5
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test HWY_EMSCRIPTEN
-- Performing Test HWY_EMSCRIPTEN - Failed
-- Performing Test HWY_RISCV
-- Performing Test HWY_RISCV - Failed
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/highway_build

$ cmake --build /tmp/highway_build
[22/35] Linking CXX executable hwy_list_targets
ld: error: unable to find library -latomic
c++: error: linker command failed with exit code 1 (use -v to see invocation)
[30/35] Linking CXX executable examples/hwy_benchmark
FAILED: examples/hwy_benchmark
: && /usr/bin/c++ -O2 -g -DNDEBUG -fPIE -pie CMakeFiles/hwy_benchmark.dir/hwy/examples/benchmark.cc.o -o examples/hwy_benchmark  libhwy.a  -latomic && :
ld: error: unable to find library -latomic
c++: error: linker command failed with exit code 1 (use -v to see invocation)
[34/35] Building CXX object CMakeFiles/hwy_contrib.dir/hwy/contrib/sort/vqsort_u16d.cc.o
ninja: build stopped: subcommand failed.

[jan-wassenberg]

Thanks @jbeich for letting us know. Because the previous fix was targeted at GCC, we could skip it if(${CMAKE_CXX_COMPILER_ID} MATCHES "Clang")?

FYI I will be away on Thu/Fri.

[jbeich]

If it's targeted at GCC shouldn't the conditional be if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU") ?

[malaterre]

In cmake world "GNU" indeed designate GCC:

• https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_COMPILER_ID.html

[jan-wassenberg]

Makes sense, thanks. So how about I change it to:

if(UNIX AND NOT APPLE)
  # For GCC __atomic_store_8, see #887
  if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND NOT HWY_EMSCRIPTEN)
    target_link_libraries(hwy atomic)
  endif()

?