Issue 774 on ARM

[Marc Singer]

We're seeing the same issue (#774) with the following invocation of the ARM cross compiler. We're using v1.83 of boost.

We tried to find a way to work around it, but none of our attempts succeeded.

/opt/arm-gnu-toolchain-12.2.rel1-darwin-arm64-arm-none-eabi/bin/arm-none-eabi-g++ -c -mcpu=cortex-m4 -mthumb -mno-unaligned-access  -mfloat-abi=soft  -fdata-sections -ffunction-sections -Wno-unused-function -fno-exceptions  -Iext/boost/boost -Os -g3 -Wall -Wundef -DOS=OS_MACOS -fdiagnostics-color=always -fno-rtti --std=gnu++20 -Wno-literal-suffix -Wno-dangling-pointer -fno-threadsafe-statics  -o ../o/lib-glow/jsonito.o generics/jsonito.cc
In file included from ext/boost/boost/boost/json/src.hpp:37,
                 from generics/jsonito.cc:43:
ext/boost/boost/boost/json/impl/parse.ipp: In function 'boost::json::value boost::json::parse(string_view, std::error_code&, storage_ptr, const parse_options&)':
ext/boost/boost/boost/json/impl/parse.ipp:49:10: error: no match for 'operator=' (operand types are 'std::error_code' and 'boost::json::error_code' {aka 'boost::system::error_code'})
   49 |     ec = jec;
      |          ^~~
In file included from /opt/arm-gnu-toolchain-12.2.rel1-darwin-arm64-arm-none-eabi/arm-none-eabi/include/c++/12.2.1/bits/ios_base.h:46,
                 from /opt/arm-gnu-toolchain-12.2.rel1-darwin-arm64-arm-none-eabi/arm-none-eabi/include/c++/12.2.1/ios:42,
                 from ext/boost/boost/boost/core/detail/string_view.hpp:30,
                 from ext/boost/boost/boost/json/string_view.hpp:14,
                 from ext/boost/boost/boost/json/kind.hpp:14,
                 from ext/boost/boost/boost/json/array.hpp:14,
                 from ext/boost/boost/boost/json.hpp:15,
                 from ext/boost/boost/boost/json/src.hpp:27:
/opt/arm-gnu-toolchain-12.2.rel1-darwin-arm64-arm-none-eabi/arm-none-eabi/include/c++/12.2.1/system_error:225:7: note: candidate: 'template<class _ErrorCodeEnum> typename std::enable_if<std::is_error_code_enum<_Tp>::value, std::error_code&>::type std::error_code::operator=(_ErrorCodeEnum)'
  225 |       operator=(_ErrorCodeEnum __e) noexcept
      |       ^~~~~~~~

[Dmitry]

This appears to be another problem with detection of platform features on MacOS. @pdimov can you look into it?

[Dmitry]

Just to be sure, have you tried any of the workarounds mentioned in #774 ?

[Peter Dimov]

I suppose this is again caused by BOOST_NO_CXX11_HDR_MUTEX being defined by Boost.Config for this platform, but I've no idea why that is.

Is libstdc++ compiled as single-threaded?

[Marc Singer]

Likely. These are arm-none-eabi targets, no OS, single core, so there isn't going to be a need for threading.

I don't have a working sample anymore since I had to move on. I don't have a way to test the boost JSON code and compiler switches.

FWIW, nlohmann's library links and it doesn't require additional code when we disable exceptions. Perhaps at a later date we can return to this detail and determine whether or not the boost library is a better long-term component.

[Peter Dimov]

In that case, the solution is to define the macro BOOST_SYSTEM_DISABLE_THREADS.