220 14146 article Path: news.gmane.org!not-for-mail From: Germinolegrand Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: #pragma once Date: Thu, 23 Oct 2014 02:04:00 -0700 (PDT) Lines: 154 Approved: news@gmane.org Message-ID: References: <3d0ab5b0-73d9-434a-9ae4-cd47d8275590@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_125_1669189462.1414055040845" X-Trace: ger.gmane.org 1414055051 20796 80.91.229.3 (23 Oct 2014 09:04:11 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 23 Oct 2014 09:04:11 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCD6BLGH7YNBBAMJUORAKGQEJ4GYPBY@isocpp.org Thu Oct 23 11:04:05 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yh0-f69.google.com ([209.85.213.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XhEJO-0003HS-Nv for gclcip-std-proposals@m.gmane.org; Thu, 23 Oct 2014 11:04:02 +0200 Original-Received: by mail-yh0-f69.google.com with SMTP id c41sf1774136yho.4 for ; Thu, 23 Oct 2014 02:04:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=DK0sYKQzh/rkqHdZajqLqH+5v2nPaDnjRoyrivDymrY=; b=bF+Fv+Ni8ETir9wpsVH/rVgNcE/kD7ag2O5Grzi8vNKUUCfbAsVru2sp3NayrqCIEI 4+coE8Pf1USD8MzbMlbUoA5A/6fZxMr/gnBr/AnDj3+WUHHDiWlPHQgsSFd9Eh8ZwFVE yiGXPnI6OevdJ4zmgBU7ss2KyG4O8lMg6O8GEbx4YxUb57QKdyx685For0g72T9xq/D/ a0N2KvfKfvf+anGrkUA2gA/+nBA3nxzhNSuB1bvWUTupL6GHImgnFp33TC6kfXtmqTeb WlZlC3JRviS1/MoScfnU/Ws3pjGL9/DWdfbJDOKwXBcxg1IPKBfghZsmRQ55A2TRbtUc ySDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=DK0sYKQzh/rkqHdZajqLqH+5v2nPaDnjRoyrivDymrY=; b=QL2xsv0skT+lLlq8S0Mjbm1wuANMaGZwU0pp1vBp/sY8kP9th5n/HlaO+Dj1yMUH6A I4rVDM1yOCTz+hBLFUq2WHSe1ar6EUvCqLf/et2JTsPtNPl0st+Mfvjxdf4h0V84G3Ix 4tzYGs7iwt5ANVAR82ItyHij0vioJtT2LqwLuxaOhCsaUUJ45FkxjpdYhL7+4Z4C7qkL R2mkKb++EBqVM2iJcJlBjnsBZsE5rcZ2zBwUNy7HnCyIgc59KLktK2RjSBapP4Q8QlhU F8mNbhAa5Ow6d4xf3i2F3GIct0BJStRefpSnKJqCyzw8wuO9G69Rjn9nvRyJhZw2iHC0 QciA== X-Gm-Message-State: ALoCoQkP5V3SrNVvi/zPX0/+fYi7CsqhjXs58Sg4v1nzqMHaCJ1tpnKkaAtQSHAwWC7c67CL8KPK X-Received: by 10.52.17.170 with SMTP id p10mr2515275vdd.6.1414055041802; Thu, 23 Oct 2014 02:04:01 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.106.7 with SMTP id d7ls1096536qgf.50.gmail; Thu, 23 Oct 2014 02:04:01 -0700 (PDT) X-Received: by 10.140.19.208 with SMTP id 74mr12349qgh.19.1414055041273; Thu, 23 Oct 2014 02:04:01 -0700 (PDT) In-Reply-To: <3d0ab5b0-73d9-434a-9ae4-cd47d8275590@isocpp.org> X-Original-Sender: germinolegrand@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:14146 Archived-At: ------=_Part_125_1669189462.1414055040845 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Seriously, I'm fed up with debugging those kind of errors no compiler can= =20 even diagnose properly ! Just helped a (not so) beginner stuck with this=20 one : #ifndef CSCWRITER_H_# define CSVWRITER_H_ Erreur 88 error C2995: 'CSV::Writer &CSV::operator <<(CSV::Writer &,const T= =20 &)' : mod=C3=A8le de fonction d=C3=A9j=C3=A0 d=C3=A9fini CSVWriter.hxx 12 When you have a lot of experience you can at least think to verify those=20 sort of stuff, but hey, when you have under 2 years experience this means= =20 hours of trying to debug a link error that's in fact a quite unvisible typo= =20 in a header guard. I myself also encounter errors myself when i copy a header to start another= =20 one (without having to recode all the #include and all the namespace=20 a{namespaceb b{ boilerplate), and thanks to murphy I forget to change the= =20 header guard name, and I do not run into any problem until i eventually=20 include both headers indirectly in one compile unit. If you just wrote the= =20 second, you often remember to watch the header guards for this error, but= =20 when you did it two weeks ago, have a good day. *"It's complicated to implement from a compiler point of view so let the=20 programmer type a lot of super-murphy piece of code instead."* Seriously ? Are we talking about C or ... ? Header guards are not superior to anything the compiler can do with a=20 #pragma once equivalent, it's only a trade-off. And i would trade easily=20 sneaky link errors due to preprocessing issues for safety and simplicity. No matter how hard it is to implement, since it's perfectly feasible (as an= =20 ultimate resort, just compare the files content). Although #pragma once would be nice since it's in large use, #once would at= =20 least solve half the problem. Le mardi 21 octobre 2014 21:29:21 UTC+2, Myriachan a =C3=A9crit : > > I think that #pragma once should be standardized - at least=20 > partially/optionally/conditionally-supported. Every major compiler=20 > implements it with identical or nearly-identical semantics. > > Defining what it means for a file to be a repeat is rather simple: On=20 > platforms supporting symlinks and hard links, use unique inode numbers (+= =20 > device if needed). On other platforms, use the filename. Compilers may= =20 > assume that files don't change while compiling (i.e. if the filename=20 > matches, it can be assumed to be identical). On platforms where there=20 > exist special links to the same or parent directory, like "./" or "../" o= n=20 > NT and POSIX, this assumption can be extended to collapse these. > > By the way, why don't _Pragma and #line support concatenating multiple=20 > strings in their respective string parameters? > > Melissa > --=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/. ------=_Part_125_1669189462.1414055040845 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Seriously, I'm fed up with debugging those kind of errors = no compiler can even diagnose properly ! Just helped a (not so) beginner st= uck with this one :

#ifndef CSCWRITER_H_
# define CSVWRITER_H_

Erreur	88	error C2995: 'CSV::Writer=20
&CSV::operator <<(CSV::Writer &,const T &)' : mod=C3=
=A8le=20
de fonction d=C3=A9j=C3=A0 d=C3=A9fini	CSVWriter.hxx	12

When you hav=
e a lot of experience you can at least think to verify those sort of stuff,=
 but hey, when you have under 2 years experience this means hours of trying=
 to debug a link error that's in fact a quite unvisible typo in a header gu=
ard.

I myself also encounter errors myself when i copy a header to s=
tart another one (without having to recode all the #include and all the nam=
espace a{namespaceb b{ boilerplate), and thanks to murphy I forget to chang=
e the header guard name, and I do not run into any problem until i eventual=
ly include both headers indirectly in one compile unit. If you just wrote t=
he second, you often remember to watch the header guards for this error, bu=
t when you did it two weeks ago, have a good day.

"It's complicat=
ed to implement from a compiler point of view so let the programmer type a =
lot of super-murphy piece of code instead."
Seriously ? Are we=
 talking about C or ... ?

Header guards are  not superior to anythin=
g the compiler can do with a #pragma once equivalent, it's only a trade-off=
.. And i would trade easily sneaky link errors due to preprocessing issues f=
or safety and simplicity.

No matter how hard it is to implement, sin=
ce it's perfectly feasible (as an ultimate resort, just compare the files c=
ontent).

Although #pragma once would be nice since it's in large use=
, #once would at least solve half the problem.

Le mardi 21 octobre 2=
014 21:29:21 UTC+2, Myriachan a =C3=A9crit :
I think that #pragma once should be standardized - at lea=
st partially/optionally/conditionally-supported.  Every major com=
piler implements it with identical or nearly-identical semantics.

De=
fining what it means for a file to be a repeat is rather simple: On platfor=
ms supporting symlinks and hard links, use unique inode numbers (+ device i=
f needed).  On other platforms, use the filename.  Compilers may =
assume that files don't change while compiling (i.e. if the filename matche=
s, it can be assumed to be identical).  On platforms where there exist=
 special links to the same or parent directory, like "./" or "../" on NT an=
d POSIX, this assumption can be extended to collapse these.

By the w=
ay, why don't _Pragma and #line supp=
ort concatenating multiple strings in their respective string parameters?
Melissa

--

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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
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