[PATCH] Fix coroutine tests for libstdc++ gnu-version-namespace mode

[François Dumont]

Hi Iain

On 11/10/2023 09:30, Iain Sandoe wrote:
> Hi François,
>
>> On 11 Oct 2023, at 05:49, François Dumont <frs.dumont@gmail.com> wrote:
>> On 08/10/2023 15:59, Iain Sandoe wrote:
>>>> On 23 Sep 2023, at 21:10, François Dumont <frs.dumont@gmail.com> wrote:
>>>>
>>>> I'm eventually fixing those tests the same way we manage this problem in libstdc++ testsuite.
>>>>
>>>>     testsuite: Add optional libstdc++ version namespace in expected diagnostic
>>>>
>>>>      When libstdc++ is build with --enable-symvers=gnu-versioned-namespace diagnostics are
>>>>      showing this namespace, currently __8.
>>>>
>>>>      gcc/testsuite/ChangeLog:
>>>>
>>>>              * testsuite/g++.dg/coroutines/coro-bad-alloc-00-bad-op-new.C: Add optional
>>>>              '__8' version namespace in expected diagnostic.
>>>>              * testsuite/g++.dg/coroutines/coro-bad-alloc-01-bad-op-del.C: Likewise.
>>>>              * testsuite/g++.dg/coroutines/coro-bad-alloc-02-no-op-new-nt.C: Likewise.
>>>>              * testsuite/g++.dg/coroutines/coro-bad-grooaf-01-grooaf-expected.C: Likewise.
>>>>              * testsuite/g++.dg/coroutines/pr97438.C: Likewise.
>>>>              * testsuite/g++.dg/coroutines/ramp-return-b.C: Likewise.
>>>>
>>>> Tested under Linux x86_64.
>>>>
>>>> I'm contributing to libstdc++ so I already have write access.
>>>>
>>>> Ok to commit ?
>>> As author of the tests, this LGTM as a suitable fix for now (at least, once the main
>>> patch to fix versioned namespaces lands).
>> I just realized it was a "go", no ? Then why after the main patch ?
>>
>> The "main patch" do not fix the versioned namespace. It just makes it adopt the cxx11 abi.
>>
>> This patch fixes a problem that is as old as the tests and that is totally unrelated with the main one. I just wanted to improve the situation so that versioned namespace mode do not look more buggy than necessary when someone (like you) run those.
> Maybe a misunderstanding on my part.  I was under the impression that versioned-namespace was currently unusable because it forces the old string ABI.  If that is not the case, then I guess the changes are OK now.

Said this way it sure makes this mode usability quite limited.

It's only functional to (almost) pass make check-c++ :-)

>
> I am pretty concerned about the maintainability of this tho, hence this …
>
>>> However, IMO, this could become quite painful as more g++ tests make use of std headers
>>> (which is not really optional for facilities like this that are tightly-coupled between the FE and
>>> the library).
>>>
>>> For the future, it does seem that a more complete solution might be to introduce a
>>> testsuite-wide definition for the C++ versioned std:: introducer, so that we can update it in one
>>> place as the version changes.
>>>
>>> So (as a thought experiment):
>>>   - we’d have something of the form “CXX_STD” as a tcl global
>>>   - we’d add the presence/absence of versioning to the relevant site.exp (which
>>>     means recognising the versioning choice also in the GCC configure)
>>>   - we’d migrate tests to using ${CXX_STD} instead of "std::__N”  in matches
>>>
>>> … I guess an alternative could be to cook up some alternate warning/error/etc
>>>     match functions that cater for arbitrary inline namespaces but that seems like a much
>>>     more tricky and invasive testsuite change.
>>>
>>> thoughts?
>> I considered amending gcc/testsuite/lib/prune.exp to simply remove the version from the diagnostic. But the reply on why it was not working scared me, so this patch.
>>
>> https://gcc.gnu.org/pipermail/gcc/2023-September/242526.html
> Ah, I didn’t see that mail - will try to take a look at the weekend.

Ok, I'll instead chase for the patches on libstdc++ side then.

Moreover adopting cxx11 abi in versioned-namespace mode will imply a 
version bump which would force to patch those files again if we do not 
find another approach before.

Thanks,

François