Can't build GTSAM with Boost 1.56 with C++11

[Chris Beall]

Errors about binding optional lvalue references:

C:\local\boost_1_56_0\boost/optional/optional.hpp(188): error C2338: binding rvalue references to optional lvalue references is disallowed (..\..\gtsam\symbolic\SymbolicFactorGraph.cpp)
3>          C:\local\boost_1_56_0\boost/optional/optional.hpp(777) : see reference to function template instantiation 'void boost::optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T,gtsam::Ordering&&>(void)' being compiled
3>          with
3>          [
3>              T=const gtsam::Ordering &
3>          ]
3>          C:\local\boost_1_56_0\boost/optional/optional.hpp(776) : while compiling class template member function 'boost::optional<T>::optional(gtsam::Ordering &&)'
3>          with
3>          [
3>              T=const gtsam::Ordering &
3>          ]
3>          C:\Users\Chris\git\gtsam\gtsam/inference/EliminateableFactorGraph-inst.h(56) : see reference to function template instantiation 'boost::optional<T>::optional(gtsam::Ordering &&)' being compiled
3>          with
3>          [
3>              T=const gtsam::Ordering &
3>          ]
3>          C:\Users\Chris\git\gtsam\gtsam/inference/EliminateableFactorGraph-inst.h(32) : see reference to class template instantiation 'boost::optional<T>' being compiled
3>          with
3>          [
3>              T=const gtsam::Ordering &
3>          ]
3>          C:\Users\Chris\git\gtsam\gtsam/inference/EliminateableFactorGraph-inst.h(32) : while compiling class template member function 'boost::shared_ptr<T> gtsam::EliminateableFactorGraph<FACTORGRAPH>::eliminateSequential(gtsam::EliminateableFactorGraph<FACTORGRAPH>::OptionalOrdering,const boost::function<Signature> &,gtsam::EliminateableFactorGraph<FACTORGRAPH>::OptionalVariableIndex) const'
3>          with
3>          [
3>              T=gtsam::SymbolicBayesNet,
3>              FACTORGRAPH=gtsam::SymbolicFactorGraph,
3>              Signature=std::pair<boost::shared_ptr<gtsam::SymbolicConditional>,boost::shared_ptr<gtsam::SymbolicFactor::This>> (const gtsam::SymbolicFactorGraph &,const gtsam::Ordering &)
3>          ]
3>          C:\Users\Chris\git\gtsam\gtsam/symbolic/SymbolicFactorGraph.h(58) : see reference to class template instantiation 'gtsam::EliminateableFactorGraph<FACTORGRAPH>' being compiled
3>          with
3>          [
3>              FACTORGRAPH=gtsam::SymbolicFactorGraph
3>          ]

[Andrew Melim]

Also on VS2013

[Andrew Melim]

This is a boost assertion being thrown due to the following

"Rvalue references and lvalue references to const have the ability in C++ to extend the life time of a temporary they bind to. Optional references do not have this capability, therefore to avoid surprising effects it is not possible to initialize an optional references from a temporary. Optional rvalue references are disabled altogether. Also, the initialization and assignment of an optional reference to const from rvalue reference is disabled."

http://www.boost.org/doc/libs/1_56_0/libs/optional/doc/html/boost_optional/tutorial/optional_references.html

[Andrew Melim]

@cbeall3 Can you try compiling this with a C++11 compiler on a non-MS compiler to reproduce? This seems to be a boost issue, regardless of the compiler.

[Andrew Melim]

Without a major re-write, there is no real way to get around this issue. I'm adding a check in cmake to define the variable

BOOST_OPTIONAL_ALLOW_BINDING_TO_RVALUES

in the preprocessor to disable the boost assertion. Unit tests pass with the definition, but I think support for 1.56 should be given cautiously for now.

[Frank Dellaert]

@cbeall3 is this still an issue?

[Chris Beall]

Yes, we still have this workaround. With Boost 1.59 the flag to disable is BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES

From http://www.boost.org/doc/libs/1_59_0/boost/optional/optional.hpp

template <class To, class From>
void prevent_binding_rvalue_ref_to_optional_lvalue_ref()
{
#ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES
  BOOST_STATIC_ASSERT_MSG(
    !boost::is_lvalue_reference<To>::value || !boost::is_rvalue_reference<From>::value, 
    "binding rvalue references to optional lvalue references is disallowed");
#endif    
}

[Frank Dellaert]

But, does that not mean this issue can be closed?