220 41225 article Path: news.gmane.org!.POSTED!not-for-mail From: =?UTF-8?Q?Klaim_=2D_Jo=C3=ABl_Lamotte?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Modules and preambule, just why? 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[209.85.220.41]) by mx.google.com with SMTPS id w14sor12496593vsa.44.2018.12.05.13.54.19 for (Google Transport Security); Wed, 05 Dec 2018 13:54:19 -0800 (PST) Received-SPF: pass (google.com: domain of mjklaim@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a67:41c2:: with SMTP id x63mr12051306vsf.185.1544046858921; Wed, 05 Dec 2018 13:54:18 -0800 (PST) In-Reply-To: X-Original-Sender: mjklaim@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="e/LWPNYY"; spf=pass (google.com: domain of mjklaim@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=mjklaim@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:41225 Archived-At: Adding to Ville's comments: On Wed, 5 Dec 2018 at 19:47, wrote: > Still, one question remains for me: > If for example you wanna ship a library. > As of today, you generally with the library the headers so that people us= ing the library will be able to compile their code and make use of the libr= ary you made. You are focusing specifically on the shared-library case, ok. Just note that it's not always the best solution for all libraries or users. > But how does it work if you wanna use modules? do you ship a module file = together with the lib? And if so, how do you intend to generate this module= file? Just ship a module interface unit that only contain the exported names marked, if implemented separately, as exported/imported symbols too. That's where it's interesting to have a module interface unit only contain the exported names+symbols. ///////////////////////////////////////////////////////////////////////////= / //// Module interface: mymodule.mxx export module mymodule; // MYMODULE_API does the export/import dance, or look at build2's __symexport as another way to do this. export namespace mymodule { // export all the names in this namespace scope class Kikoo; // Name exported but not symbol import/export: we don't want the user to use it's interface, just see it's name because it's used in other interfaces MYMODULE_API Kikoo& foo(); // name exported but also symbol import/exp= ort MYMODULE_API void bar(Kikoo&); // name exported but also symbol import/export template struct Lol { ... }; // Template, so no need to export symbols, it might benefit from less compile time for the user though. } ////////////////////////////////////////////////// ////// Module implementation : mymodule.cpp module mymodule:impl; // If I remember correctly, that's a module partition, not sure about the syntax // Just implement everything here. namespace mymodule{ class Kikoo { ... }; Kikoo& foo() { ... } void bar(Kikoo&) { ... } } ////////////////////////////////////////////////////// I'm not sure of the exact syntax so bear with me, but basically once you build that in a shared library, you just have to provide mymodule.mxx to the user, with the shared library binary (and maybe a ..lib on Windows). You can try that in the library example using build2+msvc I linked to, just move the implementation in a separate module file with the same module name but not exporting. The test is setup to link with the library, shared mode by default, so if the test work, it correctly only used the module interface and linked to it. > Also note that even if I better understand the proposal now, my doubts ab= out it and the need of declaring the module explicitly remains. No problem with that, we can probably help clarifying or maybe you can find a pain point before it gets standardized. > In fact, I would have prefer an approach where the exported symbols are d= educed from the code instead of having to declare it explicitly. As pointed before, modules aren't related with linking. Though once they are available, we will finally have a clearer way to specify in C++ the boundaries of a library. With this, it might be possible later to help with the symbol export/import, but that seems complicated as it imply specifying some stuffs that are currently unspecified. A. Jo=C3=ABl Lamotte --=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/CAOU91OOsk6-3cHUYiFA7UGtcNrpjbNdSROQ3PqeAJW%3DH0= 6rgYA%40mail.gmail.com. .