Building CXX objects fails when compiling Poisson demo

UnitSquareMesh was first introduced in DOLFIN 1.1.0 but it looks like you are using DOLFIN 1.0.0. However, it is strange that you have this problem since it looks like you are using the demo that was shipped with DOLFIN 1.0.0, which should of course work fine with 1.0.0.

Could you try to build and run the demo from the installation directory instead of the source directory? You should find them under /home/icam01/Software/FEniCS/share/dolfin/demo (assuming you have installed FEniCS in /home/icam01/Software/FEniCS).

Yes, I have Dolfin 1.0.0. Not sure what you asked. But I ran the cahn-hilliard demo as an extra check and I got problems once again. However, UnitSquare appears this time. I provided the path to the directories where the headers reside. But yet the problem persists:

/home/icam01/Software/FEniCS/share/dolfin/demo/pde/cahn-hilliard/cpp/main.o||In function `main':|
main.cpp|| undefined reference to `dolfin::init(int, char**)'|
main.cpp|| undefined reference to `dolfin::UnitSquare::UnitSquare(unsigned int, unsigned int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
main.cpp|| undefined reference to `dolfin::Constant::Constant(double)'|
main.cpp|| undefined reference to `dolfin::Constant::Constant(double)'|
main.cpp|| undefined reference to `dolfin::Constant::Constant(double)'|
main.cpp|| undefined reference to `dolfin::Constant::operator double() const'|
main.cpp|| undefined reference to `dolfin::NewtonSolver::NewtonSolver(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
main.cpp|| undefined reference to `dolfin::Parameters::operator[](std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
main.cpp|| undefined reference to `dolfin::Parameters::operator[](std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
main.cpp|| undefined reference to `dolfin::Parameters::operator[](std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
main.cpp|| undefined reference to `dolfin::Parameters::operator[](std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
main.cpp|| undefined reference to `dolfin::File::File(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
main.cpp|| undefined reference to `dolfin::Function::operator[](unsigned int) const'|
main.cpp|| undefined reference to `dolfin::Constant::operator double() const'|
main.cpp|| undefined reference to `dolfin::Function::vector()'|
main.cpp|| undefined reference to `dolfin::Function::vector()'|
main.cpp|| undefined reference to `dolfin::Function::vector()'|
main.cpp|| undefined reference to `dolfin::NewtonSolver::solve(dolfin::NonlinearProblem&, dolfin::GenericVector&)'|
main.cpp|| undefined reference to `dolfin::Function::operator[](unsigned int) const'|
main.cpp|| undefined reference to `dolfin::Function::operator[](unsigned int) const'|
main.cpp|| undefined reference to `dolfin::plot(dolfin::Function const&, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'|
main.cpp|| undefined reference to `dolfin::File::~File()'|
main.cpp|| undefined reference to `dolfin::NewtonSolver::~NewtonSolver()'|
main.cpp|| undefined reference to `dolfin::Constant::~Constant()'|
main.cpp|| undefined reference to `dolfin::Constant::~Constant()'|
main.cpp|| undefined reference to `dolfin::Constant::~Constant()'|
main.cpp|| undefined reference to `dolfin::NewtonSolver::~NewtonSolver()'|
main.cpp|| undefined reference to `dolfin::NewtonSolver::~NewtonSolver()'|
main.cpp|| undefined reference to `dolfin::File::~File()'|
main.cpp|| undefined reference to `dolfin::File::~File()'|
main.cpp|| undefined reference to `dolfin::File::~File()'|
main.cpp|| undefined reference to `dolfin::NewtonSolver::~NewtonSolver()'|
main.cpp|| undefined reference to `dolfin::Constant::~Constant()'|
main.cpp|| undefined reference to `dolfin::Constant::~Constant()'|
main.cpp|| undefined reference to `dolfin::Constant::~Constant()'|
/home/icam01/Software/FEniCS/share/dolfin/demo/pde/cahn-hilliard/cpp/main.o||In function `CahnHilliard2D::Form_0_FunctionSpace_0::Form_0_FunctionSpace_0(dolfin::Mesh const&)':|
main.cpp:(.text._ZN14CahnHilliard2D22Form_0_FunctionSpace_0C2ERKN6dolfin4MeshE[_ZN14CahnHilliard2D22Form_0_FunctionSpace_0C5ERKN6dolfin4MeshE]+0x32)||undefined reference to `cahnhilliard2d_dofmap_2::cahnhilliard2d_dofmap_2()'|
main.cpp:(.text._ZN14CahnHilliard2D22Form_0_FunctionSpace_0C2ERKN6dolfin4MeshE[_ZN14CahnHilliard2D22Form_0_FunctionSpace_0C5ERKN6dolfin4MeshE]+0x8d)||undefined reference to `dolfin::DofMap::DofMap(boost::shared_ptr<ufc::dofmap const>, dolfin::Mesh const&)'|
main.cpp:(.text._ZN14CahnHilliard2D22Form_0_FunctionSpace_0C2ERKN6dolfin4MeshE[_ZN14CahnHilliard2D22Form_0_FunctionSpace_0C5ERKN6dolfin4MeshE]+0xd4)||undefined reference to `cahnhilliard2d_finite_element_2::cahnhilliard2d_finite_element_2()'|
main.cpp:(.text._ZN14CahnHilliard2D22Form_0_FunctionSpace_0C2ERKN6dolfin4MeshE[_ZN14CahnHilliard2D22Form_0_FunctionSpace_0C5ERKN6dolfin4MeshE]+0x11c)||undefined reference to `dolfin::FiniteElement::FiniteElement(boost::shared_ptr<ufc::finite_element const>)'|
main.cpp:(.text._ZN14CahnHilliard2D22Form_0_FunctionSpace_0C2ERKN6dolfin4MeshE[_ZN14CahnHilliard2D22Form_0_FunctionSpace_0C5ERKN6dolfin4MeshE]+0x15f)||undefined reference to `dolfin::FunctionSpace::FunctionSpace(boost::shared_ptr<dolfin::Mesh const>, boost::shared_ptr<dolfin::FiniteElement const>, boost::shared_ptr<dolfin::GenericDofMap const>)'|
/home/icam01/Software/FEniCS/share/dolfin/demo/pde/cahn-hilliard/cpp/main.o||In function `CahnHilliard2D::Form_0_FunctionSpace_0::~Form_0_FunctionSpace_0()':|
main.cpp:(.text._ZN14CahnHilliard2D22Form_0_FunctionSpace_0D2Ev[_ZN14CahnHilliard2D22Form_0_FunctionSpace_0D5Ev]+0x1f)||undefined reference to `dolfin::FunctionSpace::~FunctionSpace()'|
/home/icam01/Software/FEniCS/share/dolfin/demo/pde/cahn-hilliard/cpp/main.o||In function `CahnHilliard2D::Form_0::Form_0(boost::shared_ptr<dolfin::FunctionSpace const>)':|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0x25)||undefined reference to `dolfin::Form::Form(unsigned int, unsigned int)'|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0x4f)||undefined reference to `dolfin::CoefficientAssigner::CoefficientAssigner(dolfin::Form&, unsigned int)'|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0x6e)||undefined reference to `dolfin::CoefficientAssigner::CoefficientAssigner(dolfin::Form&, unsigned int)'|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0x8d)||undefined reference to `dolfin::CoefficientAssigner::CoefficientAssigner(dolfin::Form&, unsigned int)'|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0xac)||undefined reference to `dolfin::CoefficientAssigner::CoefficientAssigner(dolfin::Form&, unsigned int)'|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0xcb)||undefined reference to `dolfin::CoefficientAssigner::CoefficientAssigner(dolfin::Form&, unsigned int)'|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0x107)||undefined reference to `cahnhilliard2d_form_0::cahnhilliard2d_form_0()'|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0x177)||undefined reference to `dolfin::CoefficientAssigner::~CoefficientAssigner()'|
main.cpp:(.text._ZN14CahnHilliard2D6Form_0C2EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE[_ZN14CahnHilliard2D6Form_0C5EN5boost10shared_ptrIKN6dolfin13FunctionSpaceEEE]+0x18e)||undefined reference to `dolfin::CoefficientAssigner::~CoefficientAssigner()'|
||More errors follow but not being shown.|
||Edit the max errors limit in compiler options...|
||=== Build finished: 50 errors, 0 warnings ===|

I'm not sure, but it looks like you might be mixing different versions of DOLFIN. Maybe it would be better if you upgraded to DOLFIN 1.1.0 (if you don't need 1.0.0 for some reason). You will need the development version of Dorsal to build version 1.1.0. You can get this by running

  bzr branch lp:dorsal