Now addNodes also adds an implicit dependency from the declaration node
to the definition node, and returns a data structure representing the
two nodes: declaration and definition.
This commits wraps all the machinery that can mutate a DependencyGraph
inside the interval factory class DependencyGraph::Builder.
In this way, once a DependencyGraph is created, it cannot be mutated by
accident from outside.
This is important because mutating it from outside makes it easy to
break the consistency of internal maps.
This risk will only increase when supporting artificial struct wrapper
types, so we encapsulate this now to prevent issues in the future.
This data structure is used to bind together a pair of pointers to
TypeDependencyNode, one referring to a declaration of a type and the
other referring to a definition of the same type.
The definition can be null if the type referred to is a type without an
explicit definition (e.g. typedefs), while it's never null for types
for which have forward declaration that is separate from the definition
(e.g. structs and unions).
This commit adds two enum entries to TypeNode::Kind to represent forward
declarations and definitions of artificial struct wrappers, that are not
present in the model but that we're forced to print in C to overcome
its limitations in representing types.
At the moment, this is only going to be used for representing return
types of RawFunctionDefinitions whose Layout returns RegisterSet, which
can't be represented in C without a wrapper.
Alessandro Di Federico