[Development] #pragma once

[Alexander Nassian]

Besides its possible flaws, it‘s simply nothing that the C++ standard defines. I also want to use some glibc features that maybe also commonly available but it is still not standard, even worse, the implementation is completely userdefined. That same discussion raises up once a year about STL containers and others and then some compiler proves that Qt‘s way is the better by introducing some kind of bug or binary incompatibility.

Beste Grüße / Best regards,
Alexander Nassian

> Am 24.01.2018 um 12:32 schrieb Jean-Michaël Celerier <jeanmichael.celerier at gmail.com>:
> 
> I certainly have been bitten much more times by include guards that were the same in different files (especially in old libraries where guards look like #ifdef QUEUE_H because of course there is a single queue.h file in the whole world, or because someone just copy-pasted the content of a file to another and forgot changing include guards -- I plead guilty!) than whatever hypothetic bug in pragma once GCC's implementation may have. 
> 
> Are there people here who had, just once, a bug due to #pragma once ? I never met any. Across network drives, with precompiled headers, unity builds, with MSVC, Clang, GCC, ccache, distcc and Icecream...
> 
> 
> 
> -------
> Jean-Michaël Celerier
> http://www.jcelerier.name
> 
>> On Wed, Jan 24, 2018 at 11:34 AM, Mitch Curtis <mitch.curtis at qt.io> wrote:
>> 
>> 
>> > -----Original Message-----
>> > From: Ville Voutilainen [mailto:ville.voutilainen at gmail.com]
>> > Sent: Wednesday, 24 January 2018 11:25 AM
>> > To: Alexander Nassian <nassian at bitshift-dynamics.com>
>> > Cc: Mitch Curtis <mitch.curtis at qt.io>; development at qt-project.org
>> > Subject: Re: [Development] #pragma once
>> >
>> > On 24 January 2018 at 12:22, Alexander Nassian <nassian at bitshift-
>> > dynamics.com> wrote:
>> > > Maybe because it’s not part of the C++ standard?
>> >
>> > #pragma once is not a replacement for include guards.
>> 
>> Why not?
>> 
>> > It's not part of the C++ standard because it doesn't always work
>> 
>> In which ways? My quick search gave me these:
>> 
>> https://stackoverflow.com/a/1946730/904422
>> https://en.wikipedia.org/wiki/Pragma_once#Caveats
>> 
>> There's also this answer that highly recommends against it, but seems quite contended in the comments:
>> 
>> https://stackoverflow.com/a/34884735/904422
>> 
>> > and modules are a superior solution anyway.
>> 
>> How so?
>> _______________________________________________
>> Development mailing list
>> Development at qt-project.org
>> http://lists.qt-project.org/mailman/listinfo/development
> 

-- 
 


—

bitshift dynamics GmbH
Neudorfer Str. 1, 79541 Lörrach
Registergericht: Amtsgericht Freiburg i. Breisgau, HRB 713747
Geschäftsführer: Alexander Nassian, Markus Pfaffinger

http://www.bitshift-dynamics.de

Zentrale: +49 762158673 - 0
Fax: +49 7621 58673 - 90

Allgemeine Anfragen: info at bitshift-dynamics.com
Technischer Support: support at bitshift-dynamics.com
Buchhaltung: invoice at bitshift-dynamics.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.qt-project.org/pipermail/development/attachments/20180124/2bfc0a05/attachment.html>