On Oct 29, 2013, at 19:14 , Richard Trieu <[email protected]> wrote:
> With these points in mind, are there particular concerns about cases where
> the “CFG won’t check all the code a Sema based warning would”. If you
> addressed the last point, I think you’d pretty much get the coverage that you
> want. What do you think?
>
> I think that globals and global initializers are not represented in the CFG.
> That's my main concern about using only the CFG at the moment.
I don't think it would be difficult to build a CFG from a single global
initializer (or member initializer). No one's done it yet, but I don't think
that means it can't be done.
On the more general issue I can see both sides: avoiding extra walks over the
AST or CFG is good, knowing what's trivially dead code is good (except when it
isn't), and not conflating concerns is good.
For these particular checks, though (and I haven't looked at the patch, just
the checks), I think they are fundamentally syntactic checks, not
flow-sensitive ones, and that we will actually get little benefit out of using
this information to improve the CFG. Each case is warning about a
likely-incorrect boolean expression, which implies that if the user fixed the
expression we could easily get a different CFG. That doesn't help answer
questions of general policy, but it might at least untangle this patch from the
discussion.
Jordan
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