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electronicarts / dem-bones

An automated algorithm to extract the linear blend skinning (LBS) from a set of example poses
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Returning reference to temporary(results in seg fault or undefined behavior) #4

Closed syoyo closed 4 years ago

syoyo commented 4 years ago

gcc 7.4.0 reports an warning to this line

https://github.com/electronicarts/dem-bones/blob/2ab9b0447ad4b8bf4a141b9c65af717e7e2c2e0f/include/DemBones/DemBones.h#L297

Returning reference to temporary triggers segmentation fault or undefined behavior. Work around is creating an variable. 

        VectorX x0 = w.col(i).toDense().cwiseMax(0.0);
        x=indexing_vector(x0, idx.head(nnzi));

Although it is better to fix not returning temp address in Indexing.h

/home/syoyo/work/dem-bones/include/DemBones/Indexing.h: In instantiation of ‘const typename ArgType::Scalar& Dem::indexing_functor_vector<ArgType, IndexType>::operator()(Eigen::Index) const [with ArgType = Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >; IndexType = Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1>; typename ArgType::Scalar = double; Eigen::Index = long int]’:
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/CoreEvaluators.h:430:110:   required from ‘Scalar Eigen::internal::nullary_wrapper<Scalar, NullaryOp, false, true, false>::operator()(const NullaryOp&, IndexType) const [with IndexType = long int; Scalar = double; NullaryOp = Dem::indexing_functor_vector<Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >, Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1> >]’
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/CoreEvaluators.h:533:37:   required from ‘Eigen::internal::evaluator<Eigen::CwiseNullaryOp<NullaryOp, PlainObjectType> >::CoeffReturnType Eigen::internal::evaluator<Eigen::CwiseNullaryOp<NullaryOp, PlainObjectType> >::coeff(IndexType) const [with IndexType = long int; NullaryOp = Dem::indexing_functor_vector<Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >, Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1> >; PlainObjectType = Eigen::Matrix<double, -1, 1>; Eigen::internal::evaluator<Eigen::CwiseNullaryOp<NullaryOp, PlainObjectType> >::CoeffReturnType = double]’
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/AssignEvaluator.h:642:5:   required from ‘void Eigen::internal::generic_dense_assignment_kernel<DstEvaluatorTypeT, SrcEvaluatorTypeT, Functor, Version>::assignCoeff(Eigen::Index) [with DstEvaluatorTypeT = Eigen::internal::evaluator<Eigen::Matrix<double, -1, 1> >; SrcEvaluatorTypeT = Eigen::internal::evaluator<Eigen::CwiseNullaryOp<Dem::indexing_functor_vector<Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >, Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1> >, Eigen::Matrix<double, -1, 1> > >; Functor = Eigen::internal::assign_op<double, double>; int Version = 0; Eigen::Index = long int]’
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/AssignEvaluator.h:501:7:   required from ‘static void Eigen::internal::dense_assignment_loop<Kernel, 1, 0>::run(Kernel&) [with Kernel = Eigen::internal::generic_dense_assignment_kernel<Eigen::internal::evaluator<Eigen::Matrix<double, -1, 1> >, Eigen::internal::evaluator<Eigen::CwiseNullaryOp<Dem::indexing_functor_vector<Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >, Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1> >, Eigen::Matrix<double, -1, 1> > >, Eigen::internal::assign_op<double, double>, 0>]’
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/AssignEvaluator.h:767:37:   required from ‘void Eigen::internal::call_dense_assignment_loop(DstXprType&, const SrcXprType&, const Functor&) [with DstXprType = Eigen::Matrix<double, -1, 1>; SrcXprType = Eigen::CwiseNullaryOp<Dem::indexing_functor_vector<Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >, Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1> >, Eigen::Matrix<double, -1, 1> >; Functor = Eigen::internal::assign_op<double, double>]’
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/AssignEvaluator.h:926:31:   [ skipping 3 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/AssignEvaluator.h:808:18:   required from ‘void Eigen::internal::call_assignment(Dst&, const Src&) [with Dst = Eigen::Matrix<double, -1, 1>; Src = Eigen::CwiseNullaryOp<Dem::indexing_functor_vector<Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >, Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1> >, Eigen::Matrix<double, -1, 1> >]’
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/PlainObjectBase.h:779:32:   required from ‘Derived& Eigen::PlainObjectBase<Derived>::_set(const Eigen::DenseBase<OtherDerived>&) [with OtherDerived = Eigen::CwiseNullaryOp<Dem::indexing_functor_vector<Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >, Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1> >, Eigen::Matrix<double, -1, 1> >; Derived = Eigen::Matrix<double, -1, 1>]’
/home/syoyo/work/dem-bones/ExtLibs/Eigen/Eigen/src/Core/Matrix.h:225:24:   required from ‘Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols>& Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols>::operator=(const Eigen::DenseBase<OtherDerived>&) [with OtherDerived = Eigen::CwiseNullaryOp<Dem::indexing_functor_vector<Eigen::CwiseBinaryOp<Eigen::internal::scalar_max_op<double, double>, const Eigen::Matrix<double, -1, 1>, const Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<double>, Eigen::Matrix<double, -1, 1> > >, Eigen::VectorBlock<Eigen::Array<int, -1, 1>, -1> >, Eigen::Matrix<double, -1, 1> >; _Scalar = double; int _Rows = -1; int _Cols = 1; int _Options = 0; int _MaxRows = -1; int _MaxCols = 1]’
/home/syoyo/work/dem-bones/include/DemBones/DemBones.h:303:6:   required from ‘void Dem::DemBones<_Scalar, _AniMeshScalar>::computeWeights() [with _Scalar = double; _AniMeshScalar = float]’
/home/syoyo/work/dem-bones/include/DemBones/DemBones.h:344:18:   required from ‘void Dem::DemBones<_Scalar, _AniMeshScalar>::compute() [with _Scalar = double; _AniMeshScalar = float]’
/home/syoyo/work/dem-bones/src/command/mainCmd.cpp:171:16:   required from here
/home/syoyo/work/dem-bones/include/DemBones/Indexing.h:106:30: warning: returning reference to temporary [-Wreturn-local-addr]
   return m_arg(m_indices[idx]);
binhhuyle commented 4 years ago

It should not be an issue because m_arg[] and m_indices[] are references to external memory, they are not allocated by indexing_functor.