From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: Simon Marchi <simon.marchi@polymtl.ca>
Cc: Manfred <mx2927@gmail.com>,
gdb@sourceware.org, "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Re: gdb 8.x - g++ 7.x compatibility
Date: Wed, 07 Feb 2018 15:19:00 -0000 [thread overview]
Message-ID: <CAH6eHdSxiEZdJLYvnwUJDbYHm2UGCR5D33VA34=LM13yvteDTw@mail.gmail.com> (raw)
In-Reply-To: <1b58e2df-5425-4f22-510c-d2e9f51040ba@polymtl.ca>
On 4 February 2018 at 05:01, Simon Marchi wrote:
> On 2018-02-03 13:35, Manfred wrote:
>> n4659 17.4 (Type equivalence) p1.3:
>>
>> Two template-ids refer to the same class, function, or variable if
>> ...
>> their corresponding non-type template arguments of integral or
>> enumeration type have identical values
>> ...
>>
>> It looks that for non-type template arguments the template type
>> equivalence is based on argument /value/ not /type/ (and value), so
>> IMHO gcc is correct where it considers foo<10u> and foo<10> to be the
>> same type, i.e. "refer to the same class"
>>
>> FWIW, type_info reports the same class name for both templates, which
>> appears to be correct as per the above.
>>
>> I would think someone from gcc might be more specific on why both
>> templates print 4294967286, and what debug info is actually stored by
>> -g in this case.
>
> I think that Roman's example clearly shows that they are not equivalent in
> all cases.
>
> Building Roman's example with g++ 7.3 results in a single instantiated type. You
> can see that both "new foo<10>()" and "new foo<10u>()" end up calling the same
> constructor. It seems like which type is instantiated depends on which template
> parameter (the signed or unsigned one) you use first. So with this:
>
> base * fi = new foo<10>();
> base * fu = new foo<10u>();
>
> the output is -10 for both, and with
>
> base * fu = new foo<10u>();
> base * fi = new foo<10>();
>
> the output is 4294967286 for both. But it's probably a bogus behavior. I tested
> with clangd, it instantiates two different types, so you get 4294967286 for the
> <10u> case and -10 for the <10> case. I also just built gcc from master, and it
> also instantiates two types, so it seems like that was fixed recently.
That was https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79092 FWIW
prev parent reply other threads:[~2018-02-07 15:19 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-03 3:17 Roman Popov
2018-02-03 3:57 ` carl hansen
2018-02-03 4:54 ` Simon Marchi
2018-02-03 5:02 ` Roman Popov
2018-02-03 6:43 ` Roman Popov
2018-02-03 14:20 ` Paul Smith
2018-02-03 17:18 ` Roman Popov
2018-02-03 18:36 ` Manfred
2018-02-04 5:02 ` Simon Marchi
2018-02-04 17:09 ` Manfred
2018-02-04 19:17 ` Martin Sebor
2018-02-05 5:07 ` Simon Marchi
2018-02-05 16:45 ` Martin Sebor
2018-02-05 16:59 ` Simon Marchi
2018-02-05 17:44 ` Roman Popov
2018-02-05 20:08 ` Jonathan Wakely
2018-02-05 20:10 ` Roman Popov
2018-02-05 20:12 ` Jonathan Wakely
2018-02-05 20:17 ` Roman Popov
2018-02-06 3:52 ` Martin Sebor
2018-02-07 7:21 ` Daniel Berlin
2018-02-07 13:44 ` Simon Marchi
2018-02-07 15:07 ` Manfred
2018-02-07 15:16 ` Jonathan Wakely
2018-02-07 16:19 ` Manfred
2018-02-07 16:26 ` Michael Matz
2018-02-07 16:43 ` Simon Marchi
2018-02-07 16:51 ` Jonathan Wakely
2018-02-07 17:03 ` Simon Marchi
2018-02-07 17:08 ` Jonathan Wakely
2018-02-07 17:20 ` Simon Marchi
2018-02-07 17:30 ` Jonathan Wakely
2018-02-07 18:28 ` Simon Marchi
2018-02-08 11:26 ` Michael Matz
2018-02-08 14:05 ` Paul Smith
2018-02-08 14:07 ` Jonathan Wakely
2018-02-07 17:31 ` Marc Glisse
2018-02-07 17:04 ` Daniel Berlin
2018-02-07 17:11 ` Daniel Berlin
2018-02-07 22:00 ` Nathan Sidwell
2018-02-07 20:29 ` Tom Tromey
2018-02-08 15:05 ` Richard Biener
2018-03-01 20:18 ` Roman Popov
2018-03-01 20:26 ` Andrew Pinski
2018-03-01 21:03 ` Jason Merrill
2018-03-02 23:06 ` Roman Popov
2018-03-03 4:01 ` Roman Popov
2018-03-04 4:28 ` Daniel Berlin
2018-02-05 11:05 ` Jonathan Wakely
2018-02-07 15:19 ` Jonathan Wakely [this message]
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