This commit removes fields from the responsibilities of `FlowVar.qll`.
The treatment of fields in that file was slow and imprecise.
It then adds another copy of the shared global data flow library, used
only to find local field flow, and it exposes that local field flow
through `localFlow` and `localFlowStep`.
This has a performance cost. It adds two cached stages to any query that
uses `localFlow`: the stage from `DataFlowImplCommon`, which is shared
with all queries that use global data flow, and a new stage just for
`localFlowStep`.
Because `ConstructorFieldInit` (member initializer lists) are not part
of the control flow graph, there was no data flow from the initial value
of parameters to their uses in member initializers. This commit adds the
necessary flow under the assumption that parameters are not overwritten
in member initializers.
This allows a member initializer list to be seen as a sequence of field
assignments. For example, the constructor
C() : a(taint()) { }
now has data flow similar to
C() { this.a = taint(); }
This brings the annotation style in sync with how we annotate new tests
these days. I also changed a few annotations to have different expected
outcome based on my understanding of the code.
This commit changes C++ `ConstructorCall` to behave like
`new`-expressions in Java: they are both `ExprNode`s and
`PostUpdateNodes`, and there's a "pre-update node" (here called
`PreConstructorCallNode`) to play the role of the qualifier argument
when calling a constructor.
This removes a lot of flow steps, but it all seems to be flow that was
present twice: both exiting a `PartialDefNode` and a
`DefinitionByReferenceNode`. All `DefinitionByReferenceNode`s are now
`PartialDefNode`s.
