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Re: [PATCH 1/5] Fix asymmetric comparison functions
- From: Richard Biener <rguenther at suse dot de>
- To: Yury Gribov <y dot gribov at samsung dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Andrey Belevantsev <abel at ispras dot ru>, Andrew MacLeod <amacleod at redhat dot com>, Andrew Pinski <pinskia at gmail dot com>, Diego Novillo <dnovillo at google dot com>, Geoff Keating <geoffk at geoffk dot org>, Jakub Jelinek <jakub at redhat dot com>, Jason Merrill <jason at redhat dot com>, Steven Bosscher <steven at gcc dot gnu dot org>
- Date: Thu, 17 Dec 2015 12:59:39 +0100 (CET)
- Subject: Re: [PATCH 1/5] Fix asymmetric comparison functions
- Authentication-results: sourceware.org; auth=none
- References: <5672787D dot 6040105 at samsung dot com> <56727936 dot 4030605 at samsung dot com> <alpine dot LSU dot 2 dot 11 dot 1512171239260 dot 3571 at t29 dot fhfr dot qr> <5672A0D1 dot 2040207 at samsung dot com>
On Thu, 17 Dec 2015, Yury Gribov wrote:
> On 12/17/2015 02:41 PM, Richard Biener wrote:
> > On Thu, 17 Dec 2015, Yury Gribov wrote:
> >
> > > Some obvious symmetry fixes.
> > >
> > > Cc-ing
> > > * Andrey (Belevantsev) for bb_top_order_comparator
> > > * Andrew (MacLeod) for compare_case_labels
> > > * Andrew (Pinski) for resort_field_decl_cmp
> > > * Diego for pair_cmp
> > > * Geoff for resort_method_name_cmp
> > > * Jakub for compare_case_labels
> > > * Jason for method_name_cmp
> > > * Richard for insert_phi_nodes_compare_var_infos, compare_case_labels
> > > * Steven for cmp_v_in_regset_pool
> >
> > So for compare_case_labels we only ever have one label with
> > !CASE_LOW - which means you only run into the case that needs
> > !CASE_LOW && !CASE_LOW if comparing an element with itself, correct?
> >
> > In this case (missing "same element" handling rather than symmetry
> > fixing) I'd prefer a
> >
> > if (case1 == case2)
> > return 0;
> >
> > So just to confirm - do the patches also contain same element
> > compare fixings?
>
> Yes, that's a fix for same element. How about adding if + gcc_assert that
> both cases can't be NULL otherwise?
Well, does qsort require the compare function to result in zero
for same elements when the sequence to be sorted doesn't contain
duplicates?
If an assert works for you that hints at these places found via static
analysis rather than a runtime fuzzer?
Richard.