On Mon, May 13, 2024 at 6:00 PM Iain Sandoe <i...@sandoe.co.uk> wrote: > > > > > 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?
I don't understand. If we set CXX to g++ -std=c++11 and ISL checks for -std=c++17 why does it then fail to add that to CXXFLAGS? > 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 >
