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Re: Implement -Wduplicated-branches (PR c/64279) (v3)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>
- Cc: Marek Polacek <polacek at redhat dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Joseph Myers <joseph at codesourcery dot com>
- Date: Tue, 1 Nov 2016 14:53:58 +0100
- Subject: Re: Implement -Wduplicated-branches (PR c/64279) (v3)
- Authentication-results: sourceware.org; auth=none
- References: <20161019110707.GJ2576@redhat.com> <20161020102835.GM2576@redhat.com> <20161024141018.GD5939@redhat.com> <20161025135919.GJ5939@redhat.com> <CADzB+2nFxXywkHK5dVWKR9i9zKCwne6YWKdo531xynGFVpB6Rw@mail.gmail.com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
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