A recent change limits c++20 requirement to libcxx: https://github.com/apache/nuttx/pull/10860 The owner of libcxx decided not to support the build of libcxx by an old compiler, It's very hard to sync with the last libcxx version, and keep the support of the old compiler at the same time in the long term.
On Thu, Oct 12, 2023 at 7:31 AM Tomek CEDRO <to...@cedro.info> wrote: > On Thu, Oct 12, 2023 at 12:19 AM Nathan Hartman wrote: > > On Wed, Oct 11, 2023 at 3:21 PM Tomek CEDRO wrote: > > > Hello world, > > > I have encountered a basic esp32:nsh build error in nuttx-12.3.0-RC0 > > > related to xtensa g++ 8.4.0 compiler: > > > xtensa-esp32-elf-g++: error: unrecognized command line option > > > '-std=gnu++20'; did you mean '-std=gnu++2a'? > > > > This was changed in d6453cfc3cd4771a5221528cab3056660be4b1e3 (PR # 8244). > > > > See mail thread: > > https://lists.apache.org/thread/rkq99os8ql28bv1w8fy5mdqwl3h2vp6m > > > > The workaround is to set Kconfig CXX_STANDARD to gnu++2a instead of > gnu++20. > > Thank you Nathan :-) > > I am following the mailing list and github PRs so I know this was > recent change to make better compatibility with C++ and this is fine > to have this support. But this should not happen at the cost of > standard build setup and/or enforcing specific compilers / versions to > everyone by default (see inviolables). This probably also impacts > other platforms/architectures, especially the older ones. I am sure > this can be fixed easily. > > I am sorry for giving my first -1 as I know there are many new > features and improvements in the RC, but I am afraid if we don't fix > that compiler problem now then there will be no incentive to do this > in future. > > > > It would be nice if the build system could automatically detect the > > compiler version and set this value accordingly and automatically, > > without a Kconfig. IIRC there are programs in tools that determine > > compiler options based on the compiler and version. (Can't remember > > details off the top of my head at the moment.) > > Yes that would be perfect! > > Quick search shows that people do this in many ways by calling > compiler with a list of flags and checking return status for each flag > to see if it is supported. > > Current C++ standards supported by GCC and CLANG are listed here: > https://gcc.gnu.org/projects/cxx-status.html > https://clang.llvm.org/cxx_status.html > > Quote from GCC: > C++20 Support in GCC > GCC has experimental support for the latest revision of the C++ > standard, which was published in 2020. The status of C++20 library > features is described in the library documentation. > C++20 features are available since GCC 8. To enable C++20 support, add > the command-line parameter -std=c++20 (use -std=c++2a in GCC 9 and > earlier) to your g++ command line. Or, to enable GNU extensions in > addition to C++20 features, add -std=gnu++20. > > Maybe a simple check can be added to a Makefile? > > Maybe a C++ support could be added as option that is disabled by > default (+compiler check)? > > > > > REMARKS: > > > 1. flock is a new system build dependency. > > > > I think documentation needs to be updated? I think not all systems > > have flock. Is it a Linux-only thing? (Non-BSD?) > > Not a big deal I guess :-) As compared to 12.2.1 in order to build > 12.3.0-RC0 I had to install additional "flock" application. It comes > from Linux and it is available on FreeBSD. On macOS (BSD) it is not > part of the base system too and it can be installed with brew. It > seems to be fairly old commit that fixes parallel build (which I also > use). Just a notice :-) > > > https://github.com/apache/nuttx-apps/blob/91a682f11bba1a537bd095cef45f17db57c9e7b9/Make.defs#L157 > > https://github.com/apache/nuttx-apps/commit/f774e8ee7202a61bcf64a93b2f3ddfd240288cf1 > > Thank you :-) > Tomek > > -- > CeDeROM, SQ7MHZ, http://www.tomek.cedro.info >
