From: Patrick Palka <ppalka@redhat.com>
To: gcc-patches@gcc.gnu.org
Cc: libstdc++@gcc.gnu.org, Patrick Palka <ppalka@redhat.com>
Subject: [PATCH] libstdc++: invalid default init in _CachedPosition [PR101231]
Date: Tue, 13 Jul 2021 15:07:21 -0400 [thread overview]
Message-ID: <20210713190721.659161-1-ppalka@redhat.com> (raw)
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(-)
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
next reply other threads:[~2021-07-13 19:07 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-13 19:07 Patrick Palka [this message]
2021-07-15 19:58 ` Jonathan Wakely
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