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Re: Implement -Wduplicated-branches (PR c/64279) (v3)


On Tue, Nov 01, 2016 at 09:41:20AM -0400, Jason Merrill wrote:
> On Tue, Oct 25, 2016 at 9:59 AM, Marek Polacek <polacek@redhat.com> wrote:
> > On Mon, Oct 24, 2016 at 04:10:21PM +0200, Marek Polacek wrote:
> >> On Thu, Oct 20, 2016 at 12:28:36PM +0200, Marek Polacek wrote:
> >> > I found a problem with this patch--we can't call do_warn_duplicated_branches in
> >> > build_conditional_expr, because that way the C++-specific codes might leak into
> >> > the hasher.  Instead, I should use operand_equal_p, I think.  Let me rework
> >> > that part of the patch.
> 
> Hmm, is there a reason not to use operand_equal_p for
> do_warn_duplicated_branches as well?  I'm concerned about hash
> collisions leading to false positives.

If the hashing function is iterative_hash_expr / inchash::add_expr, then
that is supposed to pair together with operand_equal_p, we even have
checking verification of that.

	Jakub


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