https://gcc.gnu.org/g:b07ff1f34c0e74b7d812baa1bd5987ba2c8b9625
commit r13-9498-gb07ff1f34c0e74b7d812baa1bd5987ba2c8b9625
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Mar 26 11:47:05 2025 +0000
libstdc++: Replace use of std::min in ranges::uninitialized_xxx algos
[PR101587]
Because ranges can have any signed integer-like type as difference_type,
it's not valid to use std::min(diff1, diff2). Instead of calling
std::min with an explicit template argument, this adds a new __mindist
helper that determines the common type and uses that with std::min.
libstdc++-v3/ChangeLog:
PR libstdc++/101587
* include/bits/ranges_uninitialized.h (__detail::__mindist):
New function object.
(ranges::uninitialized_copy, ranges::uninitialized_copy_n)
(ranges::uninitialized_move, ranges::uninitialized_move_n): Use
__mindist instead of std::min.
*
testsuite/20_util/specialized_algorithms/uninitialized_copy/constrained.cc:
Check ranges with difference difference types.
*
testsuite/20_util/specialized_algorithms/uninitialized_move/constrained.cc:
Likewise.
(cherry picked from commit f4b6acfc36fb1f72fdd5bf4da208515e6495a062)
Diff:
---
libstdc++-v3/include/bits/ranges_uninitialized.h | 32 ++++++++++++++++++----
.../uninitialized_copy/constrained.cc | 13 +++++++++
.../uninitialized_move/constrained.cc | 13 +++++++++
3 files changed, 52 insertions(+), 6 deletions(-)
diff --git a/libstdc++-v3/include/bits/ranges_uninitialized.h
b/libstdc++-v3/include/bits/ranges_uninitialized.h
index 386170d2a289..a77365a470a1 100644
--- a/libstdc++-v3/include/bits/ranges_uninitialized.h
+++ b/libstdc++-v3/include/bits/ranges_uninitialized.h
@@ -252,6 +252,26 @@ namespace ranges
inline constexpr __uninitialized_value_construct_n_fn
uninitialized_value_construct_n;
+ namespace __detail
+ {
+ // This is only intended for finding smaller iterator differences below,
+ // not as a general purpose replacement for std::min.
+ struct __mindist_fn
+ {
+ template<typename _Dp1, typename _Dp2>
+ constexpr common_type_t<_Dp1, _Dp2>
+ operator()(_Dp1 __d1, _Dp2 __d2) const noexcept
+ {
+ // Every C++20 iterator I satisfies weakly_incrementable<I> which
+ // requires signed-integer-like<iter_difference_t<I>>.
+ static_assert(std::__detail::__is_signed_integer_like<_Dp1>);
+ static_assert(std::__detail::__is_signed_integer_like<_Dp2>);
+ return std::min<common_type_t<_Dp1, _Dp2>>(__d1, __d2);
+ }
+ };
+ inline constexpr __mindist_fn __mindist{};
+ }
+
template<typename _Iter, typename _Out>
using uninitialized_copy_result = in_out_result<_Iter, _Out>;
@@ -274,8 +294,8 @@ namespace ranges
{
auto __d1 = __ilast - __ifirst;
auto __d2 = __olast - __ofirst;
- return ranges::copy_n(std::move(__ifirst), std::min(__d1, __d2),
- __ofirst);
+ return ranges::copy_n(std::move(__ifirst),
+ __detail::__mindist(__d1, __d2), __ofirst);
}
else
{
@@ -321,8 +341,8 @@ namespace ranges
iter_reference_t<_Iter>>)
{
auto __d = __olast - __ofirst;
- return ranges::copy_n(std::move(__ifirst), std::min(__n, __d),
- __ofirst);
+ return ranges::copy_n(std::move(__ifirst),
+ __detail::__mindist(__n, __d), __ofirst);
}
else
{
@@ -363,7 +383,7 @@ namespace ranges
auto __d2 = __olast - __ofirst;
auto [__in, __out]
= ranges::copy_n(std::make_move_iterator(std::move(__ifirst)),
- std::min(__d1, __d2), __ofirst);
+ __detail::__mindist(__d1, __d2), __ofirst);
return {std::move(__in).base(), __out};
}
else
@@ -414,7 +434,7 @@ namespace ranges
auto __d = __olast - __ofirst;
auto [__in, __out]
= ranges::copy_n(std::make_move_iterator(std::move(__ifirst)),
- std::min(__n, __d), __ofirst);
+ __detail::__mindist(__n, __d), __ofirst);
return {std::move(__in).base(), __out};
}
else
diff --git
a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_copy/constrained.cc
b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_copy/constrained.cc
index 9885d444768b..7cc9b2eb6a32 100644
---
a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_copy/constrained.cc
+++
b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_copy/constrained.cc
@@ -176,6 +176,17 @@ test03()
}
}
+void
+test_pr101587()
+{
+ short in[1];
+ __gnu_test::test_contiguous_range r(in); // difference_type is integer-like
+ long out[1];
+ std::span<long> o(out); // difference_type is ptrdiff_t
+ ranges::uninitialized_copy(r, o);
+ ranges::uninitialized_copy_n(ranges::begin(r), 0, o.begin(), o.end());
+}
+
int
main()
{
@@ -189,4 +200,6 @@ main()
test02<false>();
test02<true>();
+
+ test_pr101587();
}
diff --git
a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_move/constrained.cc
b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_move/constrained.cc
index a4343ae8f5bb..d017ccb6dc0d 100644
---
a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_move/constrained.cc
+++
b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_move/constrained.cc
@@ -186,6 +186,17 @@ test03()
}
}
+void
+test_pr101587()
+{
+ short in[1];
+ __gnu_test::test_contiguous_range r(in); // difference_type is integer-like
+ long out[1];
+ std::span<long> o(out); // difference_type is ptrdiff_t
+ ranges::uninitialized_move(r, o);
+ ranges::uninitialized_move_n(ranges::begin(r), 0, o.begin(), o.end());
+}
+
int
main()
{
@@ -199,4 +210,6 @@ main()
test02<false>();
test02<true>();
+
+ test_pr101587();
}
