From 926c36e57cebf5936f732b9d5693c399c9eb665f Mon Sep 17 00:00:00 2001
From: Maya Ogita <maya.ogita@fixstars.com>
Date: Fri, 10 Jul 2026 18:42:41 +0900
Subject: [PATCH] Fix size calculation of `xstepped_range`

---
 include/xtensor/views/xslice.hpp |  7 ++++++-
 test/test_xview.cpp              | 35 ++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/include/xtensor/views/xslice.hpp b/include/xtensor/views/xslice.hpp
index d2142fb82..cdae97c9f 100644
--- a/include/xtensor/views/xslice.hpp
+++ b/include/xtensor/views/xslice.hpp
@@ -1058,8 +1058,13 @@ namespace xt
         , m_size(size_type(0))
         , m_step(step)
     {
+        if ((step > 0 && start_val >= stop_val) || (step < 0 && start_val <= stop_val))
+        {
+            m_size = 0;
+            return;
+        }
         size_type n = stop_val - start_val;
-        m_size = n / step + (((n < 0) ^ (step > 0)) && (n % step));
+        m_size = n / step + static_cast<bool>(n % step);
     }
 
     template <class T>
diff --git a/test/test_xview.cpp b/test/test_xview.cpp
index 18449b742..6547b9df1 100644
--- a/test/test_xview.cpp
+++ b/test/test_xview.cpp
@@ -226,6 +226,41 @@ namespace xt
         EXPECT_EQ(view0, view1);
     }
 
+    TEST(xview, negative_step)
+    {
+        view_shape_type shape = {3, 4};
+        xarray<double> a(shape);
+        std::vector<double> data = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
+        std::copy(data.cbegin(), data.cend(), a.template begin<layout_type::row_major>());
+
+        auto view0 = view(a, 1, range(3, 0, -1));
+        EXPECT_EQ(size_t(1), view0.dimension());
+        EXPECT_EQ(size_t(3), view0.shape(0));
+        EXPECT_EQ(a(1, 3), view0(0));
+        EXPECT_EQ(a(1, 2), view0(1));
+        EXPECT_EQ(a(1, 1), view0(2));
+    }
+
+    TEST(xview, size_zero)
+    {
+        view_shape_type shape = {3, 4};
+        xarray<double> a(shape);
+        std::vector<double> data = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
+        std::copy(data.cbegin(), data.cend(), a.template begin<layout_type::row_major>());
+
+        auto view0 = view(a, 1, range(0, 0));
+        EXPECT_EQ(size_t(1), view0.dimension());
+        EXPECT_EQ(size_t(0), view0.shape(0));
+
+        auto view1 = view(a, 1, range(3, 0, 1));
+        EXPECT_EQ(size_t(1), view1.dimension());
+        EXPECT_EQ(size_t(0), view1.shape(0));
+
+        auto view2 = view(a, 1, range(0, 3, -1));
+        EXPECT_EQ(size_t(1), view2.dimension());
+        EXPECT_EQ(size_t(0), view2.shape(0));
+    }
+
     TEST(xview, stored_range)
     {
         view_shape_type shape = {3, 4};