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Fix dangling reference in IndexedView with expression indices

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libeigen/eigen!2335

Closes #1943
This commit is contained in:
Pavel Guzenfeld
2026-03-29 16:39:13 +00:00
committed by Rasmus Munk Larsen
parent 624ab58e8d
commit b7f6aed1b9
2 changed files with 74 additions and 0 deletions
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18
Eigen/src/Core/util/IndexedViewHelper.h
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@@ -125,6 +125,15 @@ struct SymbolicExpressionEvaluator<FixedInt<N>, SizeAtCompileTime, void> {
// Handling of generic indices (e.g. array)
//--------------------------------------------------------------------------------
// Detect Eigen expression types that are not plain objects (Matrix/Array).
// These types may hold internal references to temporaries and must be evaluated before storing.
template <typename T, typename = void>
struct is_eigen_index_expression : std::false_type {};
template <typename T>
struct is_eigen_index_expression<T, std::enable_if_t<!std::is_same<T, typename T::PlainObject>::value>>
: std::true_type {};
// Potentially wrap indices in a type that is better-suited for IndexedView evaluation.
template <typename Indices, int NestedSizeAtCompileTime, typename EnableIf = void>
struct IndexedViewHelperIndicesWrapper {
@@ -132,6 +141,15 @@ struct IndexedViewHelperIndicesWrapper {
static const type& CreateIndexSequence(const Indices& indices, Index /*nested_size*/) { return indices; }
};
// Specialization for Eigen expression types (Reshaped, Block, CwiseOp, etc.) used as indices.
// These may hold dangling references to temporaries if not evaluated.
template <typename Indices, int NestedSizeAtCompileTime>
struct IndexedViewHelperIndicesWrapper<Indices, NestedSizeAtCompileTime,
std::enable_if_t<is_eigen_index_expression<Indices>::value>> {
using type = typename Indices::PlainObject;
static type CreateIndexSequence(const Indices& indices, Index /*nested_size*/) { return indices.eval(); }
};
// Extract compile-time and runtime first, size, increments.
template <typename Indices, typename EnableIf = void>
struct IndexedViewHelper {

56
test/indexed_view.cpp
View File

@@ -840,6 +840,61 @@ void check_tutorial_examples() {
}
}
// Regression test for bug #1943: IndexedView with temporary expression indices.
void check_expression_indices() {
MatrixXd m(3, 4);
m << 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12;
// Reshaped temporary as column index (was segfault before fix).
{
auto view = m(all, Array<int, 1, 1>{0}.reshaped());
VectorXd result = view;
VERIFY_IS_APPROX(result, m.col(0));
}
// Block expression as index.
{
ArrayXi idx(3);
idx << 0, 1, 2;
auto view = m(all, idx.head(2));
MatrixXd result = view;
VERIFY_IS_APPROX(result, m.leftCols(2));
}
// CwiseBinaryOp expression as index.
{
Array<int, 2, 1> base;
base << 0, 1;
auto view = m(all, base + 0);
MatrixXd result = view;
VERIFY_IS_APPROX(result, m.leftCols(2));
}
// Reverse expression as index.
{
Array<int, 3, 1> idx;
idx << 2, 1, 0;
auto view = m(all, idx.reverse());
MatrixXd result = view;
MatrixXd expected(3, 3);
expected << m.col(0), m.col(1), m.col(2);
VERIFY_IS_APPROX(result, expected);
}
// 1D vector indexed view (VectorIndexedViewSelector path).
{
VectorXd v(5);
v << 10, 20, 30, 40, 50;
ArrayXi idx(3);
idx << 4, 2, 0;
auto view = v(idx.reverse());
VectorXd result = view;
VectorXd expected(3);
expected << 10, 30, 50;
VERIFY_IS_APPROX(result, expected);
}
}
void check_aliasing() {
Eigen::Vector<float, 5> z = {0.0f, 1.1f, 2.2f, 3.3f, 4.4f};
std::vector<int> left_indices = {0, 1, 3, 4};
@@ -854,6 +909,7 @@ EIGEN_DECLARE_TEST(indexed_view) {
CALL_SUBTEST_1(check_indexed_view());
}
CALL_SUBTEST_1(check_tutorial_examples());
CALL_SUBTEST_1(check_expression_indices());
CALL_SUBTEST_1(check_aliasing());
// static checks of some internals: