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Core: Fix dangling reference in non-const imag() of real-valued expressions

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libeigen/eigen!2682

Closes #3096

Co-authored-by: Rasmus Munk Larsen <rmlarsen@gmail.com>
This commit is contained in:
Rasmus Munk Larsen
2026-07-06 11:47:50 -07:00
co-authored by Rasmus Munk Larsen
parent b33822a2b6
commit bb18f8ad25
3 changed files with 40 additions and 2 deletions
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test/basicstuff.cpp
+27
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@@ -196,6 +196,28 @@ void basicStuffComplex(const MatrixType& m) {
VERIFY(!static_cast<const MatrixType&>(cm).imag().isZero());
}
// Regression test for issue #3096: reading imag() of a *non-const* real-valued object used to go
// through the writable CwiseUnaryView, whose functor returns a dangling reference to a temporary
// for real scalars (segfault with GCC, garbage with Clang). For real scalars the non-const imag()
// overload must return the same read-only zero expression as the const one.
template <typename MatrixType>
void basicStuffRealImag(const MatrixType& m) {
typedef typename MatrixType::RealScalar RealScalar;
Index rows = m.rows();
Index cols = m.cols();
MatrixType m1 = MatrixType::Random(rows, cols);
// Non-const lvalue.
VERIFY_IS_EQUAL(m1.imag().cwiseAbs().sum(), RealScalar(0));
// Non-const expression wrappers (temporaries), the case that used to crash.
VERIFY((m1.array().imag() == RealScalar(0)).all());
VERIFY_IS_EQUAL(m1.block(0, 0, rows, cols).imag().cwiseAbs().sum(), RealScalar(0));
// real() of a real-valued object aliases the object itself, both in the const and non-const case.
VERIFY(m1.real().data() == m1.data());
VERIFY(static_cast<const MatrixType&>(m1).real().data() == m1.data());
}
template <typename SrcScalar, typename TgtScalar>
struct casting_test {
static void run() {
@@ -347,6 +369,11 @@ EIGEN_DECLARE_TEST(basicstuff) {
MatrixXcf(internal::random<int>(1, EIGEN_TEST_MAX_SIZE), internal::random<int>(1, EIGEN_TEST_MAX_SIZE))));
CALL_SUBTEST_5(basicStuffComplex(
MatrixXcd(internal::random<int>(1, EIGEN_TEST_MAX_SIZE), internal::random<int>(1, EIGEN_TEST_MAX_SIZE))));
CALL_SUBTEST_1(basicStuffRealImag(Matrix<float, 1, 1>()));
CALL_SUBTEST_2(basicStuffRealImag(Matrix4d()));
CALL_SUBTEST_7(basicStuffRealImag(
MatrixXd(internal::random<int>(1, EIGEN_TEST_MAX_SIZE), internal::random<int>(1, EIGEN_TEST_MAX_SIZE))));
}
CALL_SUBTEST_1(fixedSizeMatrixConstruction<unsigned char>());