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Re: [C/C++ PATCH] RFC: Implement -Wduplicated-cond (PR c/64249) (take


On 09/23/2015 10:32 AM, Marek Polacek wrote:
On Tue, Sep 22, 2015 at 03:33:34PM -0600, Martin Sebor wrote:
It's fine by me (for whatever it's worth).

Thanks.  Let's wait if Jason/Joseph or anyone else wants to chime in.

Btw., if you're unhappy about having to wipe out the whole chain
after every side-effect it occurred to me that it might be possible
to do better: instead of deleting the whole chain, only remove from
it the elements that may be affected by the side-effect. This should
make it possible to keep on the chain all conditions involving local
variables whose address hasn't been taken, which I would expect to
be most in most cases.

I'm not unhappy about deleting the chain ;).  I'd rather not do that
because that might get somewhat hairy.  First, I don't think we have
the capability to easily detect variables whose address hasn't been
taken, second, consider e.g.

   if (j == 4) // ...
   else if ((j++, --k, ++l)) // ...
   else if (bar (j, &k)) // ...

we'd probably need some walk_tree, save the variables temporarily somewhere
etc.; that might slow and complicate things for a corner case.  Or am I being
just too lazy? ;)
This is all running on generic, not gimple/ssa, right? In which case, no you don't know what stuff might be aliased.

Jeff


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