Tested on x86_64-pc-linux-gnu, does this look OK for trunk and perhaps
14?
-- >8 --
Use a local reference for the (now possibly lifetime extended) result of
*__first to avoid making unnecessary copies of it.
PR libstdc++/112349
libstdc++-v3/ChangeLog:
* include/bits/ranges_algo.h (__min_fn::operator()): Turn local
object __tmp into a reference.
* include/bits/ranges_util.h (__max_fn::operator()): Likewise.
* testsuite/25_algorithms/max/constrained.cc (test04): New test.
* testsuite/25_algorithms/min/constrained.cc (test04): New test.
---
libstdc++-v3/include/bits/ranges_algo.h | 4 +--
libstdc++-v3/include/bits/ranges_util.h | 4 +--
.../25_algorithms/max/constrained.cc | 25 +++++++++++++++++++
.../25_algorithms/min/constrained.cc | 25 +++++++++++++++++++
4 files changed, 54 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/include/bits/ranges_algo.h
b/libstdc++-v3/include/bits/ranges_algo.h
index bae36637b3e..e1aba256241 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -2945,11 +2945,11 @@ namespace ranges
auto __result = *__first;
while (++__first != __last)
{
- auto __tmp = *__first;
+ auto&& __tmp = *__first;
if (std::__invoke(__comp,
std::__invoke(__proj, __result),
std::__invoke(__proj, __tmp)))
- __result = std::move(__tmp);
+ __result = std::forward<decltype(__tmp)>(__tmp);
}
return __result;
}
diff --git a/libstdc++-v3/include/bits/ranges_util.h
b/libstdc++-v3/include/bits/ranges_util.h
index 3f191e6d446..4a5349ae92a 100644
--- a/libstdc++-v3/include/bits/ranges_util.h
+++ b/libstdc++-v3/include/bits/ranges_util.h
@@ -754,11 +754,11 @@ namespace ranges
auto __result = *__first;
while (++__first != __last)
{
- auto __tmp = *__first;
+ auto&& __tmp = *__first;
if (std::__invoke(__comp,
std::__invoke(__proj, __tmp),
std::__invoke(__proj, __result)))
- __result = std::move(__tmp);
+ __result = std::forward<decltype(__tmp)>(__tmp);
}
return __result;
}
diff --git a/libstdc++-v3/testsuite/25_algorithms/max/constrained.cc
b/libstdc++-v3/testsuite/25_algorithms/max/constrained.cc
index e7269e1b734..717900656bd 100644
--- a/libstdc++-v3/testsuite/25_algorithms/max/constrained.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/max/constrained.cc
@@ -73,10 +73,35 @@ test03()
VERIFY( ranges::max({2,3,1,4}, ranges::greater{}, std::negate<>{}) == 4 );
}
+void
+test04()
+{
+ // PR libstdc++/112349 - ranges::max/min make unnecessary copies
+ static int copies, moves;
+ struct A {
+ A(int m) : m(m) { }
+ A(const A& other) : m(other.m) { ++copies; }
+ A(A&& other) : m(other.m) { ++moves; }
+ A& operator=(const A& other) { m = other.m; ++copies; return *this; }
+ A& operator=(A&& other) { m = other.m; ++moves; return *this; }
+ int m;
+ };
+ A r[5] = {5, 4, 3, 2, 1};
+ ranges::max(r, std::less{}, &A::m);
+ VERIFY( copies == 1 );
+ VERIFY( moves == 0 );
+ copies = moves = 0;
+ A s[5] = {1, 2, 3, 4, 5};
+ ranges::max(s, std::less{}, &A::m);
+ VERIFY( copies == 5 );
+ VERIFY( moves == 0 );
+}
+
int
main()
{
test01();
test02();
test03();
+ test04();
}
diff --git a/libstdc++-v3/testsuite/25_algorithms/min/constrained.cc
b/libstdc++-v3/testsuite/25_algorithms/min/constrained.cc
index 7198df69adf..d338a86f186 100644
--- a/libstdc++-v3/testsuite/25_algorithms/min/constrained.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/min/constrained.cc
@@ -73,10 +73,35 @@ test03()
VERIFY( ranges::min({2,3,1,4}, ranges::greater{}, std::negate<>{}) == 1 );
}
+void
+test04()
+{
+ // PR libstdc++/112349 - ranges::max/min make unnecessary copies
+ static int copies, moves;
+ struct A {
+ A(int m) : m(m) { }
+ A(const A& other) : m(other.m) { ++copies; }
+ A(A&& other) : m(other.m) { ++moves; }
+ A& operator=(const A& other) { m = other.m; ++copies; return *this; }
+ A& operator=(A&& other) { m = other.m; ++moves; return *this; }
+ int m;
+ };
+ A r[5] = {5, 4, 3, 2, 1};
+ ranges::min(r, std::less{}, &A::m);
+ VERIFY( copies == 5 );
+ VERIFY( moves == 0 );
+ copies = moves = 0;
+ A s[5] = {1, 2, 3, 4, 5};
+ ranges::min(s, std::less{}, &A::m);
+ VERIFY( copies == 1 );
+ VERIFY( moves == 0 );
+}
+
int
main()
{
test01();
test02();
test03();
+ test04();
}
--
2.47.0.148.g6a11438f43
