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From: "nathan at acm dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/94454] ICE 'canonical types differ for identical types'
Date: Thu, 02 Apr 2020 16:50:40 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94454

--- Comment #6 from Nathan Sidwell <nathan at acm dot org> ---
On 4/2/20 12:37 PM, iains at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94454
>=20
> --- Comment #5 from Iain Sandoe <iains at gcc dot gnu.org> ---
> (In reply to Nathan Sidwell from comment #4)
>> Oh, it is from the template specialization hash table.  I suggest making
>> that very poor to increase collisions:
>>
>> pt.c:
>> static hashval_t
>> hash_tmpl_and_args (tree tmpl, tree args)
>> {
>>    hashval_t val =3D iterative_hash_object (DECL_UID (tmpl), 0);
>>     return val; // INSERT THIS LINE
>>    return iterative_hash_template_arg (args, val);
>> }
>>
>> sorry for not realizing this earlier
>=20
> [not wishing to disturb the c-reduce sessions already started]
>=20
> On Darwin17 @r10-7488, which was always succeeding
>=20
> I bootstrapped with this patch, and then built a --disable-bootstrap with=
 the
> "spec_hasher::hash always returns 0" applied too.

Ok, BTW spec_hasher::hash forwards to hash_tmpl_and_args.  They must=20
agree, so ...

> Neither made any difference, the entire ranges-v3 suite built without iss=
ue.

surprises me.

>=20
> Maybe that's informative in its own right.
>=20
> Will hopefully have some kind of reduced test-case for x86-64-linux tomor=
row.
>=