Re: [PATCH] configure: Fix error message when C compiler is not working

[Peter Maydell]

On Fri, 8 Mar 2024 at 06:01, Thomas Huth <thuth@redhat.com> wrote:
>
> If you try to run the configure script on a system without a working
> C compiler, you get a very misleading error message:
>
>  ERROR: Unrecognized host OS (uname -s reports 'Linux')
>
> We should rather tell the user that we were not able to use the C
> compiler instead, otherwise they will have a hard time to figure
> out what was going wrong.
>
> Fixes: 264b803721 ("configure: remove compiler sanity check")
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  configure | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/configure b/configure
> index 3cd736b139..a036923dee 100755
> --- a/configure
> +++ b/configure
> @@ -411,7 +411,7 @@ else
>    # Using uname is really broken, but it is just a fallback for architectures
>    # that are going to use TCI anyway
>    cpu=$(uname -m)
> -  echo "WARNING: unrecognized host CPU, proceeding with 'uname -m' output 
> '$cpu'"
> +  echo "WARNING: could not determine host CPU, proceeding with 'uname -m' 
> output '$cpu'"
>  fi
>
>  # Normalise host CPU name to the values used by Meson cross files and in 
> source
> @@ -1000,10 +1000,12 @@ if test -z "$ninja"; then
>  fi
>
>  if test "$host_os" = "bogus"; then
> -    # Now that we know that we're not printing the help and that
> -    # the compiler works (so the results of the check_defines we used
> -    # to identify the OS are reliable), if we didn't recognize the
> -    # host OS we should stop now.
> +    # Now that we know that we're not printing the help, we should stop now
> +    # if we didn't recognize the host OS (or the C compiler is not working).
> +    write_c_skeleton;
> +    if ! compile_object ; then
> +        error_exit "C compiler \"$cc\" is not usable"
> +    fi
>      error_exit "Unrecognized host OS (uname -s reports '$(uname -s)')"
>  fi

I think I would prefer as a structure:

(1) suppress the "unrecognized host CPU" message if "$host_os" == "bogus"
(2) do the "check the C compiler works" test as its own test immediately
    after we print the help message (and not guarded by testing $host_os)
(3) leave the "Unrecognized host OS" check code as it is

thanks
-- PMM