220 29228 article Path: news.gmane.org!.POSTED!not-for-mail From: Patrice Roy Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: [RFC] #pragma once... yes, really... 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[2607:f8b0:400c:c08::22a]) by mx.google.com with ESMTPS id l26si4083416uaa.230.2016.10.28.18.04.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 28 Oct 2016 18:04:16 -0700 (PDT) Received-SPF: pass (google.com: domain of patricer@gmail.com designates 2607:f8b0:400c:c08::22a as permitted sender) client-ip=2607:f8b0:400c:c08::22a; Original-Received: by mail-ua0-x22a.google.com with SMTP id 12so67313293uas.2 for ; Fri, 28 Oct 2016 18:04:16 -0700 (PDT) X-Received: by 10.176.16.78 with SMTP id g14mr13752877uab.5.1477703056324; Fri, 28 Oct 2016 18:04:16 -0700 (PDT) Original-Received: by 10.176.85.89 with HTTP; Fri, 28 Oct 2016 18:04:15 -0700 (PDT) In-Reply-To: <8422f73d-e04f-49e4-aede-0399cd4d01db@isocpp.org> X-Original-Sender: patricer@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of patricer@gmail.com designates 2607:f8b0:400c:c08::22a as permitted sender) smtp.mailfrom=patricer@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:29228 Archived-At: --f403045e2f12c17c96053ff68dee Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable I've exchanged with others on this topic in the past and their positions were similar to Arthur's : they were actually worried that any proposed standard solution to this problem would deviate from existing (#pragma once) practice, which I understand (even though I personally prefer -- and use -- include guards, reserving #pragma for actual non-portable cases). This should not stop anyone from sumbitting solutions or =C2=ABsolutions=C2= =BB to the problem, but I thought it would be nice to know there would be resistance. 2016-10-28 17:52 GMT-04:00 Arthur O'Dwyer : > On Thursday, October 27, 2016 at 9:34:25 AM UTC-7, Matthew Woehlke wrote: >> >> After the recent thread rehashing this yet again, I'm sure some folks >> will be surprised to see me on the other side of the issue. However, all >> the noise got me to thinking how we might actually do this correctly... >> >> This is *not* a proposal for *unqualified* `#pragma once` [...] >> > > I'm not a Committee member, but if I were, I would strongly oppose any > proposal that tried to solve the "#pragma once" problem in any way other > than: > (1) Standardizing existing vendor practice, i.e., #pragma once; or > (2) Helping to move the Modules proposal more quickly toward > standardization. > > Remember, ordinary programmers (such as myself) can already use "#pragma > once" with every C or C++ compiler we encounter in daily practice. Relyin= g > on "#pragma once" is no weirder than relying on ,##__VA_ARGS__ > [a] or system > include paths or __builtin_unreachable() or -Wall -Werror or any of the > other things we use in our daily practice that have been "standardized" > only by vendors, not by ISO. > > Include-guards and #pragma once were originally invented to solve a > problem (breakage from double-inclusion) that in the medium term here wil= l > be solved by the Modules proposal, rendering the two existing solutions > obsolete. I strongly encourage anyone currently dealing with > double-inclusion problems to either:[b] > (1) Adopt the existing ISO Standard solution (include guards); or > (2) Adopt the existing solution documented by your compiler vendor > (#pragma once); or > (3) Adopt and/or pitch in and/or wait eagerly for the > soon-to-be-ISO-Standard solution (the Modules draft TS > ). > > Creating a *third* *legacy* solution to the double-inclusion problem > doesn't help anyone, least of all the ordinary programmers who are just > trying to figure out the best practice and use it to do their daily work. > [c] > > =E2=80=93Arthur > > [a] My kudos to Thomas K=C3=B6ppe for attempting to standardize existing > practice in N2023 > instead of > inventing a new thing. > [b] If you use any third-party headers, you have already done either (1) > or (2) anyway, whether you know it or not. (And you've probably done > *both*.) > [c] As usual, there is an XKCD for this. > > -- > 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 > email to std-proposals+unsubscribe@isocpp.org. > To post to this group, send email to std-proposals@isocpp.org. > To view this discussion on the web visit https://groups.google.com/a/ > isocpp.org/d/msgid/std-proposals/8422f73d-e04f-49e4- > aede-0399cd4d01db%40isocpp.org > > . > --=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/CAKiZDp2g8Hhb4cKEBmn2HAUE1mb5YP-gpZktwTb6310mCDQ= ivA%40mail.gmail.com. --f403045e2f12c17c96053ff68dee Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
I've exchanged with others on this topic in the p= ast and their positions were similar to Arthur's : they were actually w= orried that any proposed standard solution to this problem would deviate fr= om existing (#pragma once) practice, which I understand (even though I pers= onally prefer -- and use -- include guards, reserving #pragma for actual no= n-portable cases).

This should not stop anyone from sumbitting= solutions or =C2=ABsolutions=C2=BB to the problem, but I thought it would = be nice to know there would be resistance.

2016-10-28 17:52 GMT-04:00 Arthur O'= Dwyer <arthur.j.odwyer@gmail.com>:
On Thursday, October 27,= 2016 at 9:34:25 AM UTC-7, Matthew Woehlke wrote:
After the recent thread rehashing t= his yet again, I'm sure some folks
will be surprised to see me on the other side of the issue. However, al= l
the noise got me to thinking how we might actually do this correctly...

This is *not* a proposal for *unqualified* `#pragma once` [...]= =C2=A0

I'm not a Committee member, = but if I were, I would strongly oppose any proposal that tried to solve the= "#pragma once" problem in any way other than:
(1) Stan= dardizing existing vendor practice, i.e., #pragma once; or
(2) He= lping to move the Modules proposal more quickly toward standardization.

Remember, ordinary programmers (such as myself) can a= lready use "#pragma once" with every C or C++ compiler we encount= er in daily practice. Relying on "#pragma once" is no weirder tha= n relying on ,##__VA_ARG= S__[a] or system include paths or __builtin_unreachable() or -Wall -Werror or any of the other thing= s we use in our daily practice that have been "standardized" only= by vendors, not by ISO.

Include-guards and #pragm= a once were originally invented to solve a problem (breakage from double-in= clusion) that in the medium term here will be solved by the Modules proposa= l, rendering the two existing solutions obsolete. I strongly encourage anyo= ne currently dealing with double-inclusion problems to either:[b]
(1) Adopt the existing ISO Standard solution (incl= ude guards); or
(2) Adopt the existing solution documented by you= r compiler vendor (#pragma once); or
(3) Adopt and/or pitch in an= d/or wait eagerly for the soon-to-be-ISO-Standard solution (the Modules draft TS).

Creating a thi= rd=C2=A0legacy solution to the double-inclusion problem doesn= 9;t help anyone, least of all the ordinary programmers who are just trying = to figure out the best practice and use it to do their daily work.[c]

=E2=80=93Arthur

<= /div>
[a] My kudos to Thomas K=C3=B6ppe for attempting to standardize e= xisting practice in N2023 instead of inventing a new thing= ..
[b] If you use any third-party headers, you have alrea= dy done either (1) or (2) anyway, whether you know it or not. (And you'= ve probably done=C2=A0both.)
[c] As usual,=C2= =A0there is an XKCD for= this.

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To post to this group, send email to std-proposals@isocpp.org.
 To view this discussion on the web visit = https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/8422= f73d-e04f-49e4-aede-0399cd4d01db%40isocpp.org.

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