On Tue, 7 Nov 2023 at 10:24, Jonathan Wakely <jwak...@redhat.com> wrote: > > On Tue, 7 Nov 2023 at 10:18, Jonathan Wakely <jwak...@redhat.com> wrote: > > > > On Tue, 7 Nov 2023 at 10:04, Alexandre Oliva <ol...@adacore.com> wrote: > > > > > > [adding libstdc++@] > > > > > > On Nov 5, 2023, Mike Stump <mikest...@comcast.net> wrote: > > > > > > > Ick. > > > > > > Indeed ;-) > > > > > > > I wish there were fewer changed lines and not 1 per test > > > > case. It feels like we've painted ourselves into a corner. > > > > > > The libstdc++ testsuite took a different approach, detecting missing > > > headers (and libraries?) at error pruning time, and xfailing the tests, > > > which seems to be more in line with what you are looking for. > > > > > > That approach, though more expedient, seems more fragile to me, in that > > > an actual bug that caused headers to go missing would cause tests to be > > > silently skipped rather than fail. > > > > I don't think we XFAIL based on missing headers. We XFAIL based on a > > specific #error message in certain headers. > > > > If a header goes missing, we'll still XFAIL. > > > > > > > > I expect the set of headers, and thus of affected tests, won't by very > > > dynamic, so it's kind of a one-shot change. > > > > > > Of course new tests might be added that rely on such headers, and would > > > likely go unnoticed until someone tries them on a non-hosted libstdc++. > > > > Since GCC 13 you don't need to build a non-hosted libstdc++ to test > > it, you can just add -ffreestanding to the runtestflags. > > > > > We could alleviate this if libstdc++ headers that are not installed on > > > hosted systems issued a warning (conditional on some macro defined by > > > the testsuite, say -D_GLIBCXX_WARN_HOSTED_ONLY). > > > > That's exactly what happens (except #error not #warning) when you > > compile with -ffreestanding. > > > > > For tests aimed > > > exclusively at hosted libstdc++, we'd then use a dg directive that both > > > implied this requirement, and changed the macro definition to suppress > > > the warning. Then anyone who added a testcase that included hosted > > > headers without indicating its hostedlib requirement would get a fail > > > even when testing with a hosted libstdc++. > > > > I don't think we need to add checks for a new macro and then use that > > when testing, you can just test with -ffreestanding instead. This > > already works today. > > Ah, reading back in the thread for the context I missed, I see that > you're specifically testing a --disable-hosted-libstdcxx build. In > that case some headers really will be absent, not just > present-with-#error. But I am still not concerned about failing to > notice if a header goes unintentionally missing, because the libstdc++ > testsuite will still notice that. > > We don't prune based on "no such header" errors, so would still get > FAILs for those tests that depend on headers which are supposed to be > present for freestanding.
An alternative approach for the g++ testsuite would be to provide a set of dummy headers for the non-freestanding ones, so that all the hosted-only headers are provided by the testsuite itself, but consist of a single line: #error not available in freestanding Then match on that and XFAIL. So the individual tests themselves wouldn't need the dg-skip-if added to them, they would just automatically XFAIL if they use a hosted-only header. The difficulty would be where to add those dummy headers for <iostream>, <cstdio> etc. so that they're only found when testing a non-hosted build. Maybe libstdc++ could provide them in the build dir for the purposes of the testsuite, but not install them?
