indirect : a free-store-allocated value-type for C++

The class template indirect is proposed for addition to the C++ Standard Library.

http://open-std.org/JTC1/SC22/WG21/docs/papers/2016/p0201r1.pdf

The class template, indirect, confers value-like semantics on a free-store allocated object. An indirect<T> may hold a an object of a class publicly derived from T, and copying the indirect will copy the object of the derived type.

Using indirect a copyable composite object with polymorphic components can be written as:

    // Copyable composite with mutable polymorphic components
    class CompositeObject {
      std::indirect<IComponent1> c1_;
      std::indirect<IComponent2> c2_;

     public:
      CompositeObject(std::indirect<IComponent1> c1,
                        std::indirect<IComponent2> c2) :
                        c1_(std::move(c1)), c2_(std::move(c2)) {}

      // `indirect` propagates constness so const methods call 
      // corresponding const methods of components
      void foo() const { c1_->foo(); }
      void bar() const { c2_->bar(); }
      
      void foo() { c1_->foo(); }
      void bar() { c2_->bar(); }
    };

Submodules

Tests use the 'catch' test framework: https://github.com/philsquared/Catch.git

To get the submodule run:

    git submodule update --init

Building

The build uses cmake driven by a simple Python script. To build and run tests, run the following from the console:

  ./scripts/build.py --tests

Continuous integration

Build status (on Travis-CI):