Re: [PATCH] Do not prepend target triple to -fuse-ld=lld,mold.

[Richard Biener <rguenther@suse.de>]

On Thu, 9 Nov 2023, Tatsuyuki Ishi wrote:

> > On Nov 7, 2023, at 23:37, Richard Biener <rguenther@suse.de> wrote:
> > 
> > On Tue, 7 Nov 2023, Tatsuyuki Ishi wrote:
> > 
> >>> On Oct 16, 2023, at 18:16, Richard Biener <rguenther@suse.de> wrote:
> >>> 
> >>> On Mon, 16 Oct 2023, Tatsuyuki Ishi wrote:
> >>> 
> >>>> 
> >>>> 
> >>>>> On Oct 16, 2023, at 17:55, Richard Biener <rguenther@suse.de> wrote:
> >>>>> 
> >>>>> On Mon, 16 Oct 2023, Tatsuyuki Ishi wrote:
> >>>>> 
> >>>>>> 
> >>>>>> 
> >>>>>>> On Oct 16, 2023, at 17:39, Richard Biener <rguenther@suse.de> wrote:
> >>>>>>> 
> >>>>>>> On Mon, 16 Oct 2023, Tatsuyuki Ishi wrote:
> >>>>>>> 
> >>>>>>>> lld and mold are platform-agnostic and not prefixed with target triple.
> >>>>>>>> Prepending the target triple makes it less likely to find the intended
> >>>>>>>> linker executable.
> >>>>>>>> 
> >>>>>>>> A potential breaking change is that we no longer try to search for
> >>>>>>>> triple-prefixed lld/mold binaries anymore. However, since there doesn't
> >>>>>>>> seem to be support to build LLVM or mold with triple-prefixed executable
> >>>>>>>> names, it seems better to just not bother with that case.
> >>>>>>>> 
> >>>>>>>> 	PR driver/111605
> >>>>>>>> 
> >>>>>>>> gcc/Changelog:
> >>>>>>>> 
> >>>>>>>> 	* collect2.cc (main): Do not prepend target triple to
> >>>>>>>> 	-fuse-ld=lld,mold.
> >>>>>>>> ---
> >>>>>>>> gcc/collect2.cc | 13 ++++++++-----
> >>>>>>>> 1 file changed, 8 insertions(+), 5 deletions(-)
> >>>>>>>> 
> >>>>>>>> diff --git a/gcc/collect2.cc b/gcc/collect2.cc
> >>>>>>>> index 63b9a0c233a..c943f9f577c 100644
> >>>>>>>> --- a/gcc/collect2.cc
> >>>>>>>> +++ b/gcc/collect2.cc
> >>>>>>>> @@ -865,12 +865,15 @@ main (int argc, char **argv)
> >>>>>>>> int i;
> >>>>>>>> 
> >>>>>>>> for (i = 0; i < USE_LD_MAX; i++)
> >>>>>>>> -    full_ld_suffixes[i]
> >>>>>>>> #ifdef CROSS_DIRECTORY_STRUCTURE
> >>>>>>>> -      = concat (target_machine, "-", ld_suffixes[i], NULL);
> >>>>>>>> -#else
> >>>>>>>> -      = ld_suffixes[i];
> >>>>>>>> -#endif
> >>>>>>>> +    /* lld and mold are platform-agnostic and not prefixed with target
> >>>>>>>> +       triple.  */
> >>>>>>>> +    if (!(i == USE_LLD_LD || i == USE_MOLD_LD))
> >>>>>>>> +      full_ld_suffixes[i] = concat (target_machine, "-", ld_suffixes[i],
> >>>>>>>> +				    NULL);
> >>>>>>>> +    else
> >>>>>>>> +#endif
> >>>>>>>> +      full_ld_suffixes[i] = ld_suffixes[i];
> >>>>>>>> 
> >>>>>>>> p = argv[0] + strlen (argv[0]);
> >>>>>>>> while (p != argv[0] && !IS_DIR_SEPARATOR (p[-1]))
> >>>>>>> 
> >>>>>>> Since we later do
> >>>>>>> 
> >>>>>>> /* Search the compiler directories for `ld'.  We have protection against
> >>>>>>>  recursive calls in find_a_file.  */
> >>>>>>> if (ld_file_name == 0)
> >>>>>>> ld_file_name = find_a_file (&cpath, ld_suffixes[selected_linker], 
> >>>>>>> X_OK);
> >>>>>>> /* Search the ordinary system bin directories
> >>>>>>>  for `ld' (if native linking) or `TARGET-ld' (if cross).  */
> >>>>>>> if (ld_file_name == 0)
> >>>>>>> ld_file_name = find_a_file (&path, full_ld_suffixes[selected_linker], 
> >>>>>>> X_OK);
> >>>>>>> 
> >>>>>>> I wonder how having full_ld_suffixes[LLD|MOLD] == ld_suffixes[LLD|MOLD]
> >>>>>>> fixes anything?
> >>>>>> 
> >>>>>> Per the linked PR, the intended use case for this is when one wants to use their system lld/mold with a separately packaged cross toolchain, without requiring them to symlink their system lld/mold into the cross toolchain bin directory.
> >>>>>> 
> >>>>>> (Note that the first search is against COMPILER_PATH while the latter is 
> >>>>>> against PATH).
> >>>>> 
> >>>>> Ah.  So what about instead adding here
> >>>>> 
> >>>>> /* Search the ordinary system bin directories for mold/lld even in
> >>>>>    a cross configuration.  */
> >>>>> if (ld_file_name == 0
> >>>>>     && selected_linker == ...)
> >>>>>   ld_file_name = find_a_file (&path, ld_suffixes[selected_linker], X_OK);
> >>>>> 
> >>>>> instead?  That would keep things working in case the user has a
> >>>>> xyz-arch-mold in the system dir but uses GNU ld on the host
> >>>>> otherwise, lacking a 'mold' binary there?
> >>>>> 
> >>>>> That is, we'd only add, not change what we search for.
> >>>> 
> >>>> I considered that, but as described in commit message, it doesn?t seem anyone has created stuff named xyz-arch-lld or xyz-arch-mold. Closest is Gentoo?s symlink mentioned in this thread, but that?s xyz-arch-ld -> ld.lld/mold.
> >>>> As such, this feels like a quirk, not something we need to keep compatibility for.
> >>> 
> >>> I don't have a good idea whether this is the case or not unfortunately
> >>> so if it's my call I would err on the safe side.
> >>> 
> >>> We seem to recognize mold and lld only since GCC 12 which both are
> >>> still maintained so I think we might want to do the change on all
> >>> those branches?
> >>> 
> >>> If you feel confident there's indeed no such installs then let's go
> >>> with your original patch.
> >>> 
> >>> Thus, OK for trunk and the affected branches after a while of no
> >>> reported issues.
> >> 
> >> Hi,
> >> 
> >> Can I consider this an approval for this patch to be applied to trunk?
> > 
> > Yes.
> > 
> >> I would appreciate if this patch could be tested in GCC 14 prereleases.
> >> 
> >> I suppose backporting after no reported issues in GCC 14 would be the plan here?
> >> 
> >> Please let me know in case of misunderstandings.
> > 
> > You understood correctly.
> > 
> > Richard.
> 
> Hi Richard,
> 
> I forgot to mention that I don?t have committer / write access.
> 
> Could you help me get this patch committed? Thanks.

I pushed it to trunk sofar.

Richard.

> 
> Tatsuyuki.
> 
> >> Thanks,
> >> Tatsuyuki.
> >> 
> >>> Thanks,
> >>> Richard.
> >>> 
> >>>> The proposed change seems simple enough though, so if you consider this 
> >>>> a compatibility issue I can go for that way as well.
> >>> 
> >>>> Tatsuyuki.
> >>>> 
> >>>>> 
> >>>>> Thanks,
> >>>>> Richard.
> >>>> 
> >>>> 
> >>> 
> >>> -- 
> >>> Richard Biener <rguenther@suse.de <mailto:rguenther@suse.de> <mailto:rguenther@suse.de>>
> >>> SUSE Software Solutions Germany GmbH,
> >>> Frankenstrasse 146, 90461 Nuernberg, Germany;
> >>> GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
> >> 
> >> 
> > 
> > -- 
> > Richard Biener <rguenther@suse.de <mailto:rguenther@suse.de>>
> > SUSE Software Solutions Germany GmbH,
> > Frankenstrasse 146, 90461 Nuernberg, Germany;
> > GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)