Re: [Qemu-devel] [PATCH] configure: check that C++ compiler actually works

[Thomas Huth]

On Thu, 20 Feb 2014 15:10:16 +0000
Peter Maydell <address@hidden> wrote:

> Check that the C++ compiler works with the C compiler; if it
> does not, then don't pass CXX to the build process. This
> fixes a regression where QEMU was no longer building if the
> build environment didn't have a C++ compiler (introduced
> in commit 3144f78b, which incorrectly assumed that rules.mak
> would only see a non-empty $(CXX) if configure had actually
> found a working C++ compiler).
> 
> Signed-off-by: Peter Maydell <address@hidden>
> Reported-by: Alexey Kardashevskiy <address@hidden>
> Reported-by: Thomas Huth <address@hidden>
> ---
> Apologies for the breakage for people who were building in
> setups with no C++ compiler -- I should have tested the
> original change more thoroughly.
> 
>  configure | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/configure b/configure
> index 4648117..6829cbb 100755
> --- a/configure
> +++ b/configure
> @@ -1289,6 +1289,35 @@ else
>      error_exit "\"$cc\" either does not exist or does not work"
>  fi
> 
> +# Check that the C++ compiler exists and works with the C compiler
> +if has $cxx; then
> +    cat > $TMPC <<EOF
> +int c_function(void);
> +int main(void) { return c_function(); }
> +EOF
> +
> +    compile_object
> +
> +    cat > $TMPC <<EOF
> +extern "C" {
> +   int c_function(void);
> +}
> +int c_function(void) { return 42; }
> +EOF
> +
> +    if (cc=$cxx do_cc $QEMU_CFLAGS -o $TMPE $TMPC $TMPO $LDFLAGS); then
> +        # C++ compiler $cxx works ok with C compiler $cc
> +        :
> +    else
> +        echo "C++ compiler $cxx does not work with C compiler $cc"
> +        echo "Disabling C++ specific optional code"
> +        cxx=
> +    fi
> +else
> +    echo "No C++ compiler available; disabling C++ specific optional code"
> +    cxx=
> +fi
> +
>  # Consult white-list to determine whether to enable werror
>  # by default.  Only enable by default for git builds
>  z_version=`cut -f3 -d. $source_path/VERSION`

Works fine for me now on my system w/o C++ compiler:
Tested-by: Thomas Huth <address@hidden>