220 10141 <533B0135.2090701@gmail.com> article Path: news.gmane.org!not-for-mail From: "Paul A. Tessier" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Shouldn't the constexpr variables be treated as static by default? 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[71.192.182.216]) by mx.google.com with ESMTPSA id t9sm36164048qar.15.2014.04.01.11.11.01 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 01 Apr 2014 11:11:02 -0700 (PDT) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 In-Reply-To: X-Original-Sender: phernost@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of phernost@gmail.com designates 2607:f8b0:400d:c01::22c as permitted sender) smtp.mail=phernost@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:10141 Archived-At: This is a multi-part message in MIME format. --------------010605070300050201030905 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable On 04/01/2014 01:46 PM, David Krauss wrote: > > On 2014=E2=80=9303=E2=80=9331, at 5:48 PM, Paul A. Tessier > wrote: > >> A constexpr variable *must* have static storage at some point, it's=20 >> baked in when the program is compiled. Allowing it to be treated as=20 >> non-static creates a weird set of corner cases. > > I=E2=80=99m pretty sure you=E2=80=99re allowed to embed runtime data in a= constexpr=20 > object using mutable. > > This thread does touch on the behavior of extern constexpr, which I=20 > believe to be a defect=E2=80=A6 need to write a paper=E2=80=A6 > > You still'd get a copy from the immutable static version. The copy just=20 happens to have a mutable field, which in my opinion isn't really=20 constexpr object as much as it is a const object with a mutable field. Were basically stuck with poor semantics and too much variability on=20 something that has hard defined limits. All constexpr objects have=20 static storage, irregardless of extra features that confound their use.=20 Therefore I believe the syntax should be cleaned to show this, but we're=20 probably too far into the weeds now to ever fix this in a clear and=20 concise manner. Making all constexpr objects static by default is at=20 least a step in the right direction. --=20 ---=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. --------------010605070300050201030905 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On 04/01/2014 01:46 PM, David Krauss wrote:

On 2014=E2=80=9303=E2=80=9331, at 5:48 PM, Paul A. Tessier <= ;phe= rnost@gmail.com> wrote:

A constexpr variable must have static storage at some point, it's baked in when the program is compiled. Allowing it to be treated as non-static creates a weird set of corner cases.

I=E2=80=99m pretty sure you=E2=80=99re allowed to embed runtime = data in a constexpr object using mutable.

This thread does touch on the behavior of=C2=A0extern constexpr, which I believe to be a defect=E2=80=A6 need to write a paper=E2=80=A6



You still'd get a copy from the immutable static version. The copy just happens to have a mutable field, which in my opinion isn't really constexpr object as much as it is a const object with a mutable field.

Were basically stuck with poor semantics and too much variability on something that has hard defined limits. All cons= texpr objects have static storage, irregardless of extra features that confound their use. Therefore I believe the syntax should be cleaned to show this, but we're probably too far into the weeds now to ever fix this in a clear and concise manner. Making all constexpr objects static by default is at least a step in the right direction.

--

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