On Mon, 11 Sept 2023 at 12:59, Jonathan Wakely <jwak...@redhat.com> wrote:
> On Sun, 10 Sept 2023 at 20:31, Christophe Lyon > <christophe.l...@linaro.org> wrote: > > > > Some targets like arm-eabi with newlib and default settings rely on > > __sync_synchronize() to ensure synchronization. Newlib does not > > implement it by default, to make users aware they have to take special > > care. > > > > This makes a few tests fail to link. > > Does this mean those features are unusable on the target, or just that > users need to provide their own __sync_synchronize to use them? > IIUC the user is expected to provide them. Looks like we discussed this in the past :-) In https://gcc.gnu.org/legacy-ml/gcc-patches/2016-10/msg01632.html, see the pointer to Ramana's comment: https://gcc.gnu.org/ml/gcc-patches/2015-05/msg02751.html The default arch for arm-eabi is armv4t which is very old. When running the testsuite with something more recent (either as default by configuring GCC --with-arch=XXX or by forcing -march/-mcpu via dejagnu's target-board), the compiler generates barrier instructions and there are no such errors. For instance, here is a log with the defaults: https://git.linaro.org/toolchain/ci/base-artifacts/tcwg_gnu_embed_check_gcc/master-arm_eabi.git/tree/00-sumfiles?h=linaro-local/ci/tcwg_gnu_embed_check_gcc/master-arm_eabi and a log when we target cortex-m0 which is still a very small cpu but has barriers: https://git.linaro.org/toolchain/ci/base-artifacts/tcwg_gnu_embed_check_gcc/master-thumb_m0_eabi.git/tree/00-sumfiles?h=linaro-local/ci/tcwg_gnu_embed_check_gcc/master-thumb_m0_eabi I somehow wanted to get rid of such errors with the default configuration.... > > > > This patch requires the missing thread-fence effective target in the > > tests that need it, making them UNSUPPORTED instead of FAIL and > > UNRESOLVED. > > Some of the modified tests should not be using > __gnu_debug::_Safe_sequence_base::_M_detach_all(), because they don't > use the Debug Mode. I don't know where those linker errors come from. > For example, the 23_containers/span/*assert_neg.cc and > 26_numerics/valarray/* tests shouldn't use debug iterators or atomics. > Neither should 25_algorithms/sample/2.cc nor > 26_numerics/bit/bit.pow.two/bit_ceil_neg.cc > Ouch! I had the feeling this patch wouldn't count as obvious :-) I confess I didn't analyze the linker map for every single test updated by this patch.... I can have a deeper look based on your comment below, excluding those that look "OK" > The last three in the patch shouldn't use it either: > > > diff --git > a/libstdc++-v3/testsuite/experimental/net/timer/waitable/dest.cc > b/libstdc++-v3/testsuite/experimental/net/timer/waitable/dest.cc > > index cb818708aef..372ed6e0c00 100644 > > --- a/libstdc++-v3/testsuite/experimental/net/timer/waitable/dest.cc > > +++ b/libstdc++-v3/testsuite/experimental/net/timer/waitable/dest.cc > > @@ -18,6 +18,7 @@ > > // { dg-do run { target c++14 } } > > // { dg-add-options libatomic } > > // { dg-xfail-if "poll not available" { *-*-rtems* } } > > +// { dg-require-thread-fence "" } // needed by > __gnu_debug::_Safe_sequence_base::_M_detach_all() > > > > #include <experimental/timer> > > #include <testsuite_hooks.h> > > diff --git > a/libstdc++-v3/testsuite/experimental/net/timer/waitable/ops.cc > b/libstdc++-v3/testsuite/experimental/net/timer/waitable/ops.cc > > index ae51979c3b4..8383e0be6a4 100644 > > --- a/libstdc++-v3/testsuite/experimental/net/timer/waitable/ops.cc > > +++ b/libstdc++-v3/testsuite/experimental/net/timer/waitable/ops.cc > > @@ -18,6 +18,7 @@ > > // { dg-do run { target c++14 } } > > // { dg-add-options libatomic } > > // { dg-xfail-if "poll not available" { *-*-rtems* } } > > +// { dg-require-thread-fence "" } // needed by > __gnu_debug::_Safe_sequence_base::_M_detach_all() > > > > #include <experimental/timer> > > #include <testsuite_hooks.h> > > diff --git > a/libstdc++-v3/testsuite/experimental/polymorphic_allocator/construct_pair.cc > b/libstdc++-v3/testsuite/experimental/polymorphic_allocator/construct_pair.cc > > index 960c1d253b5..42de45619a8 100644 > > --- > a/libstdc++-v3/testsuite/experimental/polymorphic_allocator/construct_pair.cc > > +++ > b/libstdc++-v3/testsuite/experimental/polymorphic_allocator/construct_pair.cc > > @@ -16,6 +16,7 @@ > > // <http://www.gnu.org/licenses/>. > > > > // { dg-do run { target c++14 } } > > +// { dg-require-thread-fence "" } // needed by > __gnu_debug::_Safe_sequence_base::_M_detach_all() > > > > #include <experimental/memory_resource> > > #include <utility> > > > I'm concerned with how much of the testsuite is being completely > disabled for this target. > I think that depends on which "flavour" of arm-eabi we are looking at. I'm trying to cleanup some of the "obvious" failures, and that proves to be tedious: - quite a few gcc/g++ tests have problems when overriding -mcpu/-march with dejagnu's target-board - so I thought a first step could be to clean the default configuration, but as said above it targets a very old architecture > > Any tests with "debug" in the path are probably relying on the debug > mode, and any that use -D_GLIBCXX_DEBUG in dg-options are. And I > suppose it's expected that 29_atomics/* tests rely on atomic > synchronization, but it's unfortunate that those now can't be tested > for arm-eabi, and I don't understand why it only affects eight of the > that's only the "default" arm-eabi, it does not happen in other non-default arm-eabi (well I didn't check all possible cases) > atomics tests not all the other ones. > > Something doesn't seem right here. > > Thanks, Christophe
