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

[Iain Sandoe <iain@sandoe.co.uk>]

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.

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.
Iain