https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107200
Bug ID: 107200 Summary: False positive -Wdangling-pointer? Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: carlosgalvezp at gmail dot com Target Milestone: --- Hi, The following code triggers a -Wdangling-pointer on GCC 12 and GCC 13: #include <iostream> #include <Eigen/Core> Eigen::Vector2d foo() { return {1.0, 2.0}; } int main() { auto x = 0.5 * foo(); std::cout << x(0) << ", " << x(1) << std::endl; } <source>: In function 'int main()': <source>:10:23: note: unnamed temporary defined here 10 | auto x = 0.5 * foo(); | ~~~^~ In member function 'const Eigen::internal::scalar_product_op<LhsScalar, RhsScalar>::result_type Eigen::internal::scalar_product_op<LhsScalar, RhsScalar>::operator()(const LhsScalar&, const RhsScalar&) const [with LhsScalar = double; RhsScalar = double]', inlined from 'Eigen::internal::binary_evaluator<Eigen::CwiseBinaryOp<BinaryOp, Lhs, Rhs>, Eigen::internal::IndexBased, Eigen::internal::IndexBased>::CoeffReturnType Eigen::internal::binary_evaluator<Eigen::CwiseBinaryOp<BinaryOp, Lhs, Rhs>, Eigen::internal::IndexBased, Eigen::internal::IndexBased>::coeff(Eigen::Index) const [with BinaryOp = Eigen::internal::scalar_product_op<double, double>; Lhs = const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, const Eigen::Matrix<double, 2, 1> >; Rhs = const Eigen::Matrix<double, 2, 1>]' at /opt/compiler-explorer/libs/eigen/v3.3.9/Eigen/src/Core/CoreEvaluators.h:719:21, inlined from 'Eigen::DenseCoeffsBase<Derived, 0>::CoeffReturnType Eigen::DenseCoeffsBase<Derived, 0>::coeff(Eigen::Index) const [with Derived = Eigen::CwiseBinaryOp<Eigen::internal::scalar_product_op<double, double>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, const Eigen::Matrix<double, 2, 1> >, const Eigen::Matrix<double, 2, 1> >]' at /opt/compiler-explorer/libs/eigen/v3.3.9/Eigen/src/Core/DenseCoeffsBase.h:144:59, inlined from 'Eigen::DenseCoeffsBase<Derived, 0>::CoeffReturnType Eigen::DenseCoeffsBase<Derived, 0>::operator()(Eigen::Index) const [with Derived = Eigen::CwiseBinaryOp<Eigen::internal::scalar_product_op<double, double>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, const Eigen::Matrix<double, 2, 1> >, const Eigen::Matrix<double, 2, 1> >]' at /opt/compiler-explorer/libs/eigen/v3.3.9/Eigen/src/Core/DenseCoeffsBase.h:181:19, inlined from 'int main()' at <source>:11:37: /opt/compiler-explorer/libs/eigen/v3.3.9/Eigen/src/Core/functors/BinaryFunctors.h:86:128: warning: using a dangling pointer to an unnamed temporary [-Wdangling-pointer=] 86 | EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const result_type operator() (const LhsScalar& a, const RhsScalar& b) const { return a * b; } | Reproducible on Godbolt: https://godbolt.org/z/7475f7WvK The warning goes away with this change: - auto x = 0.5 * foo(); + Eigen::Vector2d x = 0.5 * foo(); What could be the reason for this behavior? Thanks!