Re: [OE-core] [PATCH] insane: Check if the C++ toolchain supports --std=gnu++20

["Antonin Godard" <antonin.godard@bootlin.com>]

Hi Yoann,

On Wed Mar 19, 2025 at 7:20 PM CET, Yoann Congal via lists.openembedded.org wrote:
> From: Yoann Congal <yoann.congal@smile.fr>
>
> This is needed to build nodejs from meta-oe. Check this early to avoid
> an error later in the build.
>
> Fixes [YOCTO #15804]
>
> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
> ---
> WARNING: as discussed in previous threads [0][1], this will disqualify
> builds on Ubuntu 20.04 (its g++ does not support the option)
> [0]: https://lists.openembedded.org/g/openembedded-devel/topic/111740469
> [1]: https://lists.yoctoproject.org/g/yocto-patches/topic/yocto_autobuilder2_patch/111757761
> ---
>  meta/classes-global/sanity.bbclass | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>
> diff --git a/meta/classes-global/sanity.bbclass b/meta/classes-global/sanity.bbclass
> index 1bae998f74..5783b92b26 100644
> --- a/meta/classes-global/sanity.bbclass
> +++ b/meta/classes-global/sanity.bbclass
> @@ -629,6 +629,28 @@ def check_cpp_toolchain(d):
>      except subprocess.CalledProcessError as e:
>          return f"An unexpected issue occurred during the C++ toolchain check: {str(e)}"
>  
> +def check_cpp_stdgnupp20_toolchain(d):
> +    """
> +    Checks if the C++ toolchain support the '--std=gnu++20' option
> +    """
> +    import shlex
> +    import subprocess
> +
> +    cpp_code = """
> +    #include <iostream>
> +    int main() {
> +        std::cout << "Hello, World!" << std::endl;
> +        return 0;
> +    }
> +    """
> +
> +    cmd = shlex.split(d.getVar("BUILD_CXX")) + ["-x", "c++","-", "-o", "/dev/null", "--std=gnu++20"]
> +    try:
> +        subprocess.run(cmd, input=cpp_code, capture_output=True, text=True, check=True)
> +        return None
> +    except subprocess.CalledProcessError as e:
> +        return f"An unexpected issue occurred during the C++ 'std=gnu++20' toolchain check: {str(e)}"
> +
>  def sanity_handle_abichanges(status, d):
>      #
>      # Check the 'ABI' of TMPDIR
> @@ -804,6 +826,9 @@ def check_sanity_version_change(status, d):
>      # Check if linking with lstdc++ is failing
>      status.addresult(check_cpp_toolchain(d))
>  
> +    # Check if the C++ toolchain supports --std=gnu++20
> +    status.addresult(check_cpp_stdgnupp20_toolchain(d))

The code in check_cpp_stdgnupp20_toolchain is very similar to
check_cpp_toolchain, maybe an opportunity to do something like
check_cpp_toolchain(d, flag)?

Antonin

-- 
Antonin Godard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com