108 lines
4.2 KiB
Diff
108 lines
4.2 KiB
Diff
commit 6f5dcea85a31845ec6f4b6886734b0f02e013718
|
|
Author: Jonathan Wakely <jwakely@redhat.com>
|
|
Date: Tue Feb 27 17:50:34 2024 +0000
|
|
|
|
libstdc++: Fix conditions for using memcmp in std::lexicographical_compare_three_way [PR113960]
|
|
|
|
The change in r11-2981-g2f983fa69005b6 meant that
|
|
std::lexicographical_compare_three_way started to use memcmp for
|
|
unsigned integers on big endian targets, but for that to be valid we
|
|
need the two value types to have the same size and we need to use that
|
|
size to compute the length passed to memcmp.
|
|
|
|
I already defined a __is_memcmp_ordered_with trait that does the right
|
|
checks, std::lexicographical_compare_three_way just needs to use it.
|
|
|
|
libstdc++-v3/ChangeLog:
|
|
|
|
PR libstdc++/113960
|
|
* include/bits/stl_algobase.h (__is_byte_iter): Replace with ...
|
|
(__memcmp_ordered_with): New concept.
|
|
(lexicographical_compare_three_way): Use __memcmp_ordered_with
|
|
instead of __is_byte_iter. Use correct length for memcmp.
|
|
* testsuite/25_algorithms/lexicographical_compare_three_way/113960.cc:
|
|
New test.
|
|
|
|
(cherry picked from commit f5cdda8acb06c20335855ed353ab9a441c12128a)
|
|
|
|
diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
|
|
index 7664301a208..6e648e48ad0 100644
|
|
--- a/libstdc++-v3/include/bits/stl_algobase.h
|
|
+++ b/libstdc++-v3/include/bits/stl_algobase.h
|
|
@@ -1780,11 +1780,14 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
|
|
}
|
|
|
|
#if __cpp_lib_three_way_comparison
|
|
- // Iter points to a contiguous range of unsigned narrow character type
|
|
- // or std::byte, suitable for comparison by memcmp.
|
|
- template<typename _Iter>
|
|
- concept __is_byte_iter = contiguous_iterator<_Iter>
|
|
- && __is_memcmp_ordered<iter_value_t<_Iter>>::__value;
|
|
+ // Both iterators refer to contiguous ranges of unsigned narrow characters,
|
|
+ // or std::byte, or big-endian unsigned integers, suitable for comparison
|
|
+ // using memcmp.
|
|
+ template<typename _Iter1, typename _Iter2>
|
|
+ concept __memcmp_ordered_with
|
|
+ = (__is_memcmp_ordered_with<iter_value_t<_Iter1>,
|
|
+ iter_value_t<_Iter2>>::__value)
|
|
+ && contiguous_iterator<_Iter1> && contiguous_iterator<_Iter2>;
|
|
|
|
// Return a struct with two members, initialized to the smaller of x and y
|
|
// (or x if they compare equal) and the result of the comparison x <=> y.
|
|
@@ -1834,20 +1837,20 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
|
|
if (!std::is_constant_evaluated())
|
|
if constexpr (same_as<_Comp, __detail::_Synth3way>
|
|
|| same_as<_Comp, compare_three_way>)
|
|
- if constexpr (__is_byte_iter<_InputIter1>)
|
|
- if constexpr (__is_byte_iter<_InputIter2>)
|
|
- {
|
|
- const auto [__len, __lencmp] = _GLIBCXX_STD_A::
|
|
- __min_cmp(__last1 - __first1, __last2 - __first2);
|
|
- if (__len)
|
|
- {
|
|
- const auto __c
|
|
- = __builtin_memcmp(&*__first1, &*__first2, __len) <=> 0;
|
|
- if (__c != 0)
|
|
- return __c;
|
|
- }
|
|
- return __lencmp;
|
|
- }
|
|
+ if constexpr (__memcmp_ordered_with<_InputIter1, _InputIter2>)
|
|
+ {
|
|
+ const auto [__len, __lencmp] = _GLIBCXX_STD_A::
|
|
+ __min_cmp(__last1 - __first1, __last2 - __first2);
|
|
+ if (__len)
|
|
+ {
|
|
+ const auto __blen = __len * sizeof(*__first1);
|
|
+ const auto __c
|
|
+ = __builtin_memcmp(&*__first1, &*__first2, __blen) <=> 0;
|
|
+ if (__c != 0)
|
|
+ return __c;
|
|
+ }
|
|
+ return __lencmp;
|
|
+ }
|
|
#endif // is_constant_evaluated
|
|
while (__first1 != __last1)
|
|
{
|
|
diff --git a/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare_three_way/113960.cc b/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare_three_way/113960.cc
|
|
new file mode 100644
|
|
index 00000000000..d51ae1a3d50
|
|
--- /dev/null
|
|
+++ b/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare_three_way/113960.cc
|
|
@@ -0,0 +1,15 @@
|
|
+// { dg-do run { target c++20 } }
|
|
+
|
|
+// PR libstdc++/113960
|
|
+// std::map with std::vector as input overwrites itself with c++20, on s390x
|
|
+
|
|
+#include <algorithm>
|
|
+#include <testsuite_hooks.h>
|
|
+
|
|
+int main()
|
|
+{
|
|
+ unsigned short a1[] { 1, 2, 3 };
|
|
+ unsigned short a2[] { 1, 2, 4 };
|
|
+ // Incorrect memcmp comparison for big endian targets.
|
|
+ VERIFY( std::lexicographical_compare_three_way(a1, a1+3, a2, a2+3) < 0 );
|
|
+}
|