Shared pointers

Note

Work in progress

Shroud has support for smart pointers. When the entry smart_pointer has values in a class, a subclass will be created in the Fortran wrapper. This shadow class holds the smart pointer instead of a pointer to an instance of the class.

declarations:
- decl: class Object
  smart_pointer:
  - type: std::shared_ptr
  - type: std::weak_ptr
  declarations:
  - decl: Object()
  - decl: ~Object()

The generated Fortran wrappers will be

type object
    type(SHA_SHROUD_capsule_data) :: cxxmem
contains
    procedure :: dtor => object_dtor
end type object

type, extends(object) :: object_shared
contains
    procedure :: dtor => object_shared_dtor
    final :: object_shared_final
end type object_shared

interface object
    module procedure object_ctor
end interface object

interface object_shared
    module procedure object_shared_ctor
end interface object_shared

To create an object in C++ with new object, call the object function. To create a shared object with std::make_shared(object), call the object_shared function.

The smart_pointer entry may have a format entry to control names in the generated code. The name of the shared object is controlled by the format field C_name_shared_api which has a default value from option C_name_shared_api_template.

The final function on object_shared will call the reset function to decrement the reference count.

Shroud will add the function use_count to operate on the shared_ptr. It can be renamed with the format field F_name_shared_use_count. If F_name_shared_use_count is blank the function will not be added.

type(object_shared) shared
type(object_weak) weak

shared = object_shared()
weak = shared
print *, shared.use_count()