[PATCH v1] libstdc++-v3: Update VTV vars for libtool link commands [PR99172]

[Jonathan Wakely]

On 12/03/21 15:33 -0800, Caroline Tice wrote:
>I have updated the patch as you suggested, to filter the
>"-fvtable-verify=std" out of AM_CXXFLAGS, and I have verified that it
>passes the testsuite with no regressions and fixes the reported bug.

This means we also don't pass it to LTCXXCOMPILE, instead of just
removing it from CXXLINK as in the original patch.  Since I have never
understood what libtool is for, I don't really know if that's OK, but
if it works then it works.

>Is this OK to commit now?

OK, thanks.

>-- Caroline Tice
>cmtice@google.com
>
>libstdc++-v3/ChangeLog
>
>2021-03-12  Caroline Tice  <cmtice@google.com>
>
>        PR libstdc++/99172
>        * src/Makefile.am (AM_CXXFLAGS_PRE, AM_CXXFLAGS): Add
>        AM_CXXFLAGS_PRE with the old definition of AM_CXXFLAGS; make
>        AM_CXXFLAGS to be AM_CXXFLAGS_PRE with '-fvtable-verify=std'
>        filtered out.
>        * src/Makefile.in: Regenerate.
>
>
>
>-- Caroline
>cmtice@google.com
>
>
>On Thu, Mar 11, 2021 at 9:10 AM Jonathan Wakely <jwakely@redhat.com> wrote:
>>
>> On 11/03/21 17:46 +0100, Jakub Jelinek via Libstdc++ wrote:
>> >On Thu, Mar 11, 2021 at 04:31:51PM +0000, Jonathan Wakely via Gcc-patches wrote:
>> >> On 11/03/21 16:27 +0000, Jonathan Wakely wrote:
>> >> > That seems cleaner to me, rather than adding another variable with
>> >> > minor differences from the existing AM_CXXFLAGS.
>> >>
>> >> My specific concern is that AM_CXXFLAGS and AM_CXXFLAGS_LT will get
>> >> out of sync, i.e. we'll add something to the former and forget to add
>> >> it to the latter.
>> >>
>> >> If we keep using AM_CXXFLAGS but cancel out the -fvtable-verify=std
>> >> option, then there aren't two separate variables that can diverge.
>> >>
>> >> But I think it's too late in the gcc-11 process for that kind of
>> >> refactoring.
>> >
>> >I think $(filter-out -fvtable-verify=std,$(AM_CXXFLAGS)) should be fairly
>> >simple thing if that is all that needs to be done.
>>
>> Yes, we could do that now, and then in stage 1 look at the other
>> changes (like moving -Wl,-u options to the link flags not cxxflags).
>>
>> Using filter-out does assume that no target is going to add anything
>> different that should also be filtered out, but that's true as of
>> today.
>>