From a10d6b5eb999a74fd4b12c00e8fb379cd3460e93 Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@redhat.com>
Date: Wed, 19 Oct 2022 13:03:25 -0400
Subject: [PATCH] libstdc++: Fix typo in stride_view's operator- [PR107313]

	PR libstdc++/107313

libstdc++-v3/ChangeLog:

	* include/std/ranges (stride_view::_Iterator::operator-): Fix typo.
	* testsuite/std/ranges/adaptors/stride/1.cc (test03): New test.
---
 libstdc++-v3/include/std/ranges               |  2 +-
 .../testsuite/std/ranges/adaptors/stride/1.cc | 20 +++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index d113cf19dc7b..b29264931cc0 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -7874,7 +7874,7 @@ namespace views::__adaptor
     friend constexpr difference_type
     operator-(default_sentinel_t __y, const _Iterator& __x)
       requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
-    { return __detail::__div_ceil(__x._M_end, __x._M_current, __x._M_stride); }
+    { return __detail::__div_ceil(__x._M_end - __x._M_current, __x._M_stride); }
 
     friend constexpr difference_type
     operator-(const _Iterator& __x, default_sentinel_t __y)
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/stride/1.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/stride/1.cc
index 745d1a61c1b9..37ae896014a5 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/stride/1.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/stride/1.cc
@@ -64,10 +64,30 @@ test02()
   VERIFY( ranges::equal(v, (int[]){1, 4, 7}) );
 }
 
+void
+test03()
+{
+  // PR libstdc++/107313
+  int x[] = {1, 2, 3, 4, 5};
+  __gnu_test::test_input_range<int> rx(x);
+  auto r = views::counted(rx.begin(), 4) | views::stride(2);
+  auto i = r.begin();
+  std::default_sentinel_t s = r.end();
+  VERIFY( s != i );
+  VERIFY( s - i == 2 && i - s == -2 );
+  ++i;
+  VERIFY( s != i );
+  VERIFY( s - i == 1 && i - s == -1 );
+  ++i;
+  VERIFY( s == i );
+  VERIFY( s - i == 0 && i - s == 0 );
+}
+
 int
 main()
 {
   static_assert(test01());
   test02<__gnu_test::test_input_range<int>>();
   test02<__gnu_test::test_forward_range<int>>();
+  test03();
 }
-- 
2.47.2