Re: [PATCH] Improve C++ header detection in configure

["Carlos O'Donell" <carlos at systemhalted dot org>]

On Thu, Nov 22, 2012 at 11:19 PM, Adam Conrad <adconrad@0c3.net> wrote:
> In Debian and Ubuntu, we recently shuffled around some of the
> C++ header locations to help multilib and multiarch co-exist
> more pleasantly.  In the process, the configure magic to try
> to find headers broke, as it assumed a rather rigid directory
> structure.
>
> The following patch replaces the rigid assumptions with
> instead grabbing the full include list, and then grepping
> for /c++/ and using the return.  This is working in current
> Ubuntu and Debian, and was further tested by Carlos to return
> correct results with older compilers back to gcc 4.2.
>
> 2012-11-22  Adam Conrad  <adconrad@0c3.net>
>
>         * configure.in: Improve search for C++ headers by not
>         assuming a uniform directory structure on all hosts.

Overly verbose. Please save this for the git log.

Suggest ": Autodetect C++ header directories."

>         * configure: Regenerated.
>
> --
> --- a/configure.in      2012-11-21 12:37:04.000000000 -0700
> +++ b/configure.in      2012-11-21 13:07:44.075825970 -0700
> @@ -1033,12 +1033,11 @@
>  -isystem `echo $sysheaders | sed 's/:/ -isystem /g'`"
>    if test -n "$CXX"; then
>      CXX_SYSINCLUDES=
> -    cxxmachine=`$CXX -dumpmachine 2>&AS_MESSAGE_LOG_FD` &&
> -    cxxheaders=`$CXX -v -S -x c++ /dev/null -o /dev/null 2>&1 \
> -       | sed -n -e '1,/#include/d' -e '/^ \//{p;q;}' | sed 's/ //'`
> -    test "x$cxxheaders" != x && test "x$i" != "x$cxxheaders" &&
> -    CXX_SYSINCLUDES="$CXX_SYSINCLUDES -isystem $cxxheaders \
> --isystem $cxxheaders/$cxxmachine -isystem $cxxheaders/backward"
> +    for cxxheaders in `$CXX -v -S -x c++ /dev/null -o /dev/null 2>&1 \
> +    | sed -n -e '1,/#include/d' -e '/^ \//{p;}' | tr -d ' ' | grep '/c++/'`; do

I think that both `sed 's/ //'` and `tr -d ' '` are wrong.

We should support paths with spaces.

What about `sed 's/^ *//'` or similar?

Roll it into the previous sed?

> +      test "x$cxxheaders" != x &&
> +      CXX_SYSINCLUDES="$CXX_SYSINCLUDES -isystem $cxxheaders"
> +    done
>    fi
>  fi
>  AC_SUBST(SYSINCLUDES)
> --
>

Cheers,
Carlos.