[cfe-dev] [Patch] Update to Checker Development Manual

[Sam Handler]

On Mon, May 6, 2013 at 8:43 PM, Jordan Rose <jordan_rose at apple.com> wrote:

> +If needed, the <tt>addTransition</tt> function can be called with no
> arguments to return the current
> +<tt>ExplodedNode</tt> without changing the program's state.
>
>
> This isn't exactly true; addTransition returns a *new* node without
> changing the *current *node's state, but it does return a new node,
> either for emitting a bug report or just putting your stamp on whatever you
> are checking. If you use addTransition just to get the current node, it's
> all to you end up splitting the path.
>

Calling addTransition without arguments does not in fact appear to return a
new node.

ExplodedNode *addTransition(ProgramStateRef State = 0,
                            const ProgramPointTag *Tag = 0) {
  return addTransitionImpl(State ? State : getState(), false, 0, Tag);
}

ExplodedNode *addTransitionImpl(ProgramStateRef State,
                               bool MarkAsSink,
                               ExplodedNode *P = 0,
                               const ProgramPointTag *Tag = 0) {
  if (!State || (State == Pred->getState() && !Tag && !MarkAsSink))
    return Pred;
  ...


Since getState() returns Pred->getState(), calling addTransition() is the
same as calling addTransitionImpl(Pred->getState(), false, 0, 0), which
will simply return Pred.

I'm not sure if this behavior is intentional, although there are many
existing checkers that call addTransition with no arguments to get the
ExplodedNode for a bug report.

In any case, I've changed the text to recommend getPredecessor(), as this
seems like the more logical choice. I've also made it clearer that this can
only be used if no state transition has been performed.

All other comments should be addressed.

--Sam


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