r210372 - Add -Wtautological-undefined-compare and -Wundefined-bool-conversion warnings

[Chandler Carruth]

On Tue, Aug 5, 2014 at 3:36 PM, Nico Weber <thakis at chromium.org> wrote:

> This is a very useful warning, thanks.
>
> One issue I have with it is that it's disabled
> by Wno-tautological-compare. From the warning name that makes sense –
> but Wtautological-compare used to be a fairly harmless warning, so we
> (chromium) disabled it for a bunch of third-party libraries. When
> Wtautological-undefined-compare arrived, we fixed all instances of this in
> our code and updated our compiler to a clang that optimizes away
> comparisons of references with NULL (since we had fixed all of these
> comparisons, we thought!)
>
> I recently realized that we didn't see Wtautological-undefined-compare
> warnings for all the third-party libraries that we're building with
> Wno-tautological-compare.
>
> Do you think Wtautological-undefined-compare should be in its own warning
> group (and maybe have a different name to make that clear), so that folks
> who disabled Wtautological-compare still get this warning? The reasoning is
> that this warning is much more serious that what Wtautological-compare used
> to warn about.
>

I don't really understand why. There is no actual undefined behavior here,
just a comparison that can never, ever be go the other way. It seems almost
exactly as severe as comparing an unsigned number for >= 0?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20140805/3330ba24/attachment.html>