| Message ID | 20210713190721.659161-1-ppalka@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | libstdc++: invalid default init in _CachedPosition [PR101231] | expand |
On Tue, 13 Jul 2021 at 20:09, Patrick Palka via Libstdc++ <libstdc++@gcc.gnu.org> wrote: > > The primary template for _CachedPosition is a dummy implementation for > non-forward ranges, the iterators for which generally can't be cached. > Because this implementation doesn't actually cache anything, _M_has_value > is defined to be false and so calls to _M_get (which are always guarded > by _M_has_value) are unreachable. > > Still, to suppress a "control reaches end of non-void function" warning > I made _M_get return {}, but after P2325 input iterators are no longer > necessarily default constructible so this workaround now breaks valid > programs. > > This patch fixes this by instead using __builtin_unreachable to squelch > the warning. > > Tested on x86_64-pc-linux-gnu, does this look OK for trunk? Yes, thanks. > > PR libstdc++/101231 > > libstdc++-v3/ChangeLog: > > * include/std/ranges (_CachedPosition::_M_get): For non-forward > ranges, just call __builtin_unreachable. > * testsuite/std/ranges/istream_view.cc (test05): New test. > --- > libstdc++-v3/include/std/ranges | 2 +- > libstdc++-v3/testsuite/std/ranges/istream_view.cc | 12 ++++++++++++ > 2 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges > index df74ac9dc19..d791e15d096 100644 > --- a/libstdc++-v3/include/std/ranges > +++ b/libstdc++-v3/include/std/ranges > @@ -1232,7 +1232,7 @@ namespace views::__adaptor > _M_get(const _Range&) const > { > __glibcxx_assert(false); > - return {}; > + __builtin_unreachable(); > } > > constexpr void > diff --git a/libstdc++-v3/testsuite/std/ranges/istream_view.cc b/libstdc++-v3/testsuite/std/ranges/istream_view.cc > index 369790e89e5..2f15f787250 100644 > --- a/libstdc++-v3/testsuite/std/ranges/istream_view.cc > +++ b/libstdc++-v3/testsuite/std/ranges/istream_view.cc > @@ -83,6 +83,17 @@ test04() > static_assert(!std::forward_iterator<It>); > } > > +void > +test05() > +{ > + // PR libstdc++/101231 > + auto words = std::istringstream{"42"}; > + auto is = ranges::istream_view<int>(words); > + auto r = is | views::filter([](auto) { return true; }); > + for (auto x : r) > + ; > +} > + > int > main() > { > @@ -90,4 +101,5 @@ main() > test02(); > test03(); > test04(); > + test05(); > } > -- > 2.32.0.170.gd486ca60a5 >
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index df74ac9dc19..d791e15d096 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -1232,7 +1232,7 @@ namespace views::__adaptor _M_get(const _Range&) const { __glibcxx_assert(false); - return {}; + __builtin_unreachable(); } constexpr void diff --git a/libstdc++-v3/testsuite/std/ranges/istream_view.cc b/libstdc++-v3/testsuite/std/ranges/istream_view.cc index 369790e89e5..2f15f787250 100644 --- a/libstdc++-v3/testsuite/std/ranges/istream_view.cc +++ b/libstdc++-v3/testsuite/std/ranges/istream_view.cc @@ -83,6 +83,17 @@ test04() static_assert(!std::forward_iterator<It>); } +void +test05() +{ + // PR libstdc++/101231 + auto words = std::istringstream{"42"}; + auto is = ranges::istream_view<int>(words); + auto r = is | views::filter([](auto) { return true; }); + for (auto x : r) + ; +} + int main() { @@ -90,4 +101,5 @@ main() test02(); test03(); test04(); + test05(); }
The primary template for _CachedPosition is a dummy implementation for non-forward ranges, the iterators for which generally can't be cached. Because this implementation doesn't actually cache anything, _M_has_value is defined to be false and so calls to _M_get (which are always guarded by _M_has_value) are unreachable. Still, to suppress a "control reaches end of non-void function" warning I made _M_get return {}, but after P2325 input iterators are no longer necessarily default constructible so this workaround now breaks valid programs. This patch fixes this by instead using __builtin_unreachable to squelch the warning. Tested on x86_64-pc-linux-gnu, does this look OK for trunk? PR libstdc++/101231 libstdc++-v3/ChangeLog: * include/std/ranges (_CachedPosition::_M_get): For non-forward ranges, just call __builtin_unreachable. * testsuite/std/ranges/istream_view.cc (test05): New test. --- libstdc++-v3/include/std/ranges | 2 +- libstdc++-v3/testsuite/std/ranges/istream_view.cc | 12 ++++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-)