Re: [PATCH] configure: respect --with-build-time-tools [PR43301]

[Eric Gallager <egall@gwmail.gwu.edu>]

On Tue, Aug 2, 2022 at 1:24 AM Alexandre Oliva <oliva@gnu.org> wrote:
>
> Hello, Eric,
>
> Thanks for looking into this.
>
> On Aug  1, 2022, Eric Gallager via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
>
> >> This just reassigns the value that was retrieved a couple of lines
> >> above from the very same variable.
>
> > Oh, ok, so I guess this isn't necessary after all?
>
> Yeah, I don't see how this patch could make any difference as to the
> reported problem.
>
> > In which case we can just close 43301 as INVALID then?
>
> AFAICT, with_build_time_tools is dealt with in the top level configure,
> setting up *_FOR_TARGET after searching for the tool names in the
> specified location.
>
> However, there's a potentially confusing consequence of the current
> code: gcc/configure looks for ./as$build_exeext in the build tree, and
> uses that without overwriting it if found, so if an earlier configure
> run created an 'as' script, a reconfigure will just use it, without
> creating the file again, even if it would have changed
> ORIGINAL_AS_FOR_TARGET in it.
>
> I suppose if the patch was tested by the original submitter on a clean
> build tree, so it would *appear* to have made a difference in fixing the
> problem, while it was actually just a no-op, and the apparent fix was a
> consequence of the clean build tree.
>
> So, the patch is not useful, but we may want to avoid the confusing
> scenario somehow.
>
> I suppose the point of not creating such a tiny script again is not to
> avoid unnecessary rebuilding of dependencies (I don't even see how
> dependencies on the script would come into play), so creating it again
> wouldn't hurt.  However, we wish to avoid overwriting an assembler
> copied into the build tree for use by gcc during the build.  Perhaps:
>
> -elif test -x as$build_exeext; then
> +elif test -x as$build_exeext \
> +       && { test "x$build_exeext" != "x" \
> +            || test "x`grep '^# Invoke as, ld or nm from the build tree' \
> +                         as`" = "x"; }; then
>
> WDYT?

Hi, thanks for the feedback; I'm a bit confused, though: where exactly
would this proposed change go?

>
> --
> Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
>    Free Software Activist                       GNU Toolchain Engineer
> Disinformation flourishes because many people care deeply about injustice
> but very few check the facts.  Ask me about <https://stallmansupport.org>