> On 13 May 2024, at 16:05, Iain Sandoe via Gcc <gcc@gcc.gnu.org> wrote:
>> On 30 Aug 2023, at 00:32, Ben Boeckel via Gcc <gcc@gcc.gnu.org> wrote:
>>
>> On Tue, Aug 29, 2023 at 18:57:37 +0200, Richard Biener wrote:
>>> I suppose for bootstrapping we could disable ISL during stage1 since
>>> it enables an optional feature only. Other than that GCC only
>>> requires a C++11 compiler for building, so ISL breaks that constraint
>>> with requiring C++17.
>>
>> Note that it doesn't *require* it per sé; the tests that try it are
>> compiled if C++17 support was detected at all. The headers seem to just
>> have optional header-only `std::any`-using APIs if C++17 is around.
>> `isl` supporting a flag to disable the tests would also work, but that
>> doesn't fix 0.26. It also doesn't mean it won't start requiring C++17 at
>> some point in the future.
>
> Perhaps, in the short-term (i.e. before it requires C++ > 11) we can
> solve this by ensuring that we pass -std=c++11 to the configure stages
> as well as to the build. ISTM that configure is finding C++17-capability
> (because we do not, I think, force C++11 for the configure) and then
> the build takes it away by forcing -std=c++11.
That was not right.
We add std=c++11 to the compiler command.
However,as noted (earlier in this thread) the isl configure has the idiom
- does the compiler do c++17 with no options?
- does the compiler do c++17 if we add -std=c++17?
where the second one overrides our setting of std=c++11 in the compiler
comand.
(I think that this is a reasonably often used idiom in configures)
However the isl configure _does_ still append CXXFLAGS, and so that if
we add -std=c++11 to those, it re-asserts our intent.
Maybe we should just add the -std=c++11 to CXXFLAGS instead of the
compiler command?
Iain
>> In light of that, I feel that skipping it for bootstrap is probably the
>> right solution here. Alas, my skill with autotools is closer to the
>> caveman-with-club level rather than that of a surgeon.
>
> I am not sure we have an easy way to exclude a host module from
> stage1 only (but ICBW).
>
> Iain
>
>>
>> --Ben
