Merge branch 'pybind:master' into master

.github/workflows/ci.yml

@@ -324,8 +324,8 @@ jobs:
   # Testing NVCC; forces sources to behave like .cu files
   cuda:
     runs-on: ubuntu-latest
-    name: "🐍 3.8 • CUDA 11.2 • Ubuntu 20.04"
+    name: "🐍 3.10 • CUDA 11.7 • Ubuntu 22.04"
-    container: nvidia/cuda:11.2.2-devel-ubuntu20.04
+    container: nvidia/cuda:11.7.0-devel-ubuntu22.04
 
     steps:
     - uses: actions/checkout@v3

include/pybind11/cast.h

@@ -1545,7 +1545,7 @@ private:
             throw cast_error_unable_to_convert_call_arg(a.name, a.type);
 #endif
         }
-        m_kwargs[a.name] = a.value;
+        m_kwargs[a.name] = std::move(a.value);
     }
 
     void process(list & /*args_list*/, detail::kwargs_proxy kp) {

include/pybind11/pybind11.h

@@ -1578,6 +1578,22 @@ public:
         return *this;
     }
 
+// Nvidia's NVCC is broken between 11.4.0 and 11.8.0
+//   https://github.com/pybind/pybind11/issues/4193
+#if defined(__CUDACC__) && (__CUDACC_VER_MAJOR__ == 11) && (__CUDACC_VER_MINOR__ >= 4)            \
+    && (__CUDACC_VER_MINOR__ <= 8)
+    template <typename T, typename... Extra>
+    class_ &def(const T &op, const Extra &...extra) {
+        op.execute(*this, extra...);
+        return *this;
+    }
+
+    template <typename T, typename... Extra>
+    class_ &def_cast(const T &op, const Extra &...extra) {
+        op.execute_cast(*this, extra...);
+        return *this;
+    }
+#else
     template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
     class_ &def(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
         op.execute(*this, extra...);
@@ -1589,6 +1605,7 @@ public:
         op.execute_cast(*this, extra...);
         return *this;
     }
+#endif
 
     template <typename... Args, typename... Extra>
     class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra &...extra) {

include/pybind11/pytypes.h

@@ -1829,18 +1829,18 @@ public:
             // guard if destructor called while err indicator is set
             error_scope error_guard;
             auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
-            if (destructor == nullptr) {
+            if (PyErr_Occurred()) {
-                if (PyErr_Occurred()) {
+                throw error_already_set();
-                    throw error_already_set();
-                }
-                pybind11_fail("Unable to get capsule context");
             }
             const char *name = get_name_in_error_scope(o);
             void *ptr = PyCapsule_GetPointer(o, name);
             if (ptr == nullptr) {
                 throw error_already_set();
             }
-            destructor(ptr);
+
+            if (destructor != nullptr) {
+                destructor(ptr);
+            }
         });
 
         if (!m_ptr || PyCapsule_SetContext(m_ptr, (void *) destructor) != 0) {

tests/test_eigen.cpp

@@ -197,11 +197,40 @@ TEST_SUBMODULE(eigen, m) {
 
     // Return a block of a matrix (gives non-standard strides)
     m.def("block",
-          [](const Eigen::Ref<const Eigen::MatrixXd> &x,
+          [m](const py::object &x_obj,
-             int start_row,
+              int start_row,
-             int start_col,
+              int start_col,
-             int block_rows,
+              int block_rows,
-             int block_cols) { return x.block(start_row, start_col, block_rows, block_cols); });
+              int block_cols) {
+              return m.attr("_block")(x_obj, x_obj, start_row, start_col, block_rows, block_cols);
+          });
+
+    m.def(
+        "_block",
+        [](const py::object &x_obj,
+           const Eigen::Ref<const Eigen::MatrixXd> &x,
+           int start_row,
+           int start_col,
+           int block_rows,
+           int block_cols) {
+            // See PR #4217 for background. This test is a bit over the top, but might be useful
+            // as a concrete example to point to when explaining the dangling reference trap.
+            auto i0 = py::make_tuple(0, 0);
+            auto x0_orig = x_obj[*i0].cast<double>();
+            if (x(0, 0) != x0_orig) {
+                throw std::runtime_error(
+                    "Something in the type_caster for Eigen::Ref is terribly wrong.");
+            }
+            double x0_mod = x0_orig + 1;
+            x_obj[*i0] = x0_mod;
+            auto copy_detected = (x(0, 0) != x0_mod);
+            x_obj[*i0] = x0_orig;
+            if (copy_detected) {
+                throw std::runtime_error("type_caster for Eigen::Ref made a copy.");
+            }
+            return x.block(start_row, start_col, block_rows, block_cols);
+        },
+        py::keep_alive<0, 1>());
 
     // test_eigen_return_references, test_eigen_keepalive
     // return value referencing/copying tests:

tests/test_eigen.py

@@ -217,15 +217,24 @@ def test_negative_stride_from_python(msg):
     )
 
 
+def test_block_runtime_error_type_caster_eigen_ref_made_a_copy():
+    with pytest.raises(RuntimeError) as excinfo:
+        m.block(ref, 0, 0, 0, 0)
+    assert str(excinfo.value) == "type_caster for Eigen::Ref made a copy."
+
+
 def test_nonunit_stride_to_python():
     assert np.all(m.diagonal(ref) == ref.diagonal())
     assert np.all(m.diagonal_1(ref) == ref.diagonal(1))
     for i in range(-5, 7):
         assert np.all(m.diagonal_n(ref, i) == ref.diagonal(i)), f"m.diagonal_n({i})"
 
-    assert np.all(m.block(ref, 2, 1, 3, 3) == ref[2:5, 1:4])
+    # Must be order="F", otherwise the type_caster will make a copy and
-    assert np.all(m.block(ref, 1, 4, 4, 2) == ref[1:, 4:])
+    # m.block() will return a dangling reference (heap-use-after-free).
-    assert np.all(m.block(ref, 1, 4, 3, 2) == ref[1:4, 4:])
+    rof = np.asarray(ref, order="F")
+    assert np.all(m.block(rof, 2, 1, 3, 3) == rof[2:5, 1:4])
+    assert np.all(m.block(rof, 1, 4, 4, 2) == rof[1:, 4:])
+    assert np.all(m.block(rof, 1, 4, 3, 2) == rof[1:4, 4:])
 
 
 def test_eigen_ref_to_python():

tests/test_pytypes.cpp

@@ -289,6 +289,12 @@ TEST_SUBMODULE(pytypes, m) {
         return capsule;
     });
 
+    m.def("return_capsule_with_explicit_nullptr_dtor", []() {
+        py::print("creating capsule with explicit nullptr dtor");
+        return py::capsule(reinterpret_cast<void *>(1234),
+                           static_cast<void (*)(void *)>(nullptr)); // PR #4221
+    });
+
     // test_accessors
     m.def("accessor_api", [](const py::object &o) {
         auto d = py::dict();

tests/test_pytypes.py

@@ -299,6 +299,17 @@ def test_capsule(capture):
     """
     )
 
+    with capture:
+        a = m.return_capsule_with_explicit_nullptr_dtor()
+        del a
+        pytest.gc_collect()
+    assert (
+        capture.unordered
+        == """
+        creating capsule with explicit nullptr dtor
+    """
+    )
+
 
 def test_accessors():
     class SubTestObject: