<div dir="ltr"><div>It is a chicken and egg problem.</div><div><br></div><div>Integrating modules in build systems will be a tedious endeavor - especially in meta build systems,</div><div>and there is little incentive to do that before modules get merged.</div><div><br></div><div>It would be rather inconvenient to realize modules are not reasonably consumed by build system _after_ the IS is published.</div><div><br></div><div>While having large modularized projects and build systems would be nice, it's a luxury we don't seem to have.</div><div>And I think taking a long look at module toolability (both in term of current tools. and in term of the 10 years goals/hopes this group has for tooling) falls in SG15 purview.</div><div><br></div><div>While my own experience is limited, I trust this group has enough build system experience and knowledge to foresee eventual issues and correct for them.</div><div>We can also extrapolate from the well-known issue of headers name collision that exists and the guidelines that arose from that. </div><div><br></div><div>It is important to be explicit about what we mean when we say "implementation experience" when talking about modules because they exist at the border between language and tools</div><div>and having compiler implementation experience isn't the whole story.</div><br><div class="gmail_quote"><div dir="ltr">On Thu, 10 Jan 2019 at 21:39 JF Bastien <<a href="mailto:cxx@jfbastien.com">cxx@jfbastien.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Thu, Jan 10, 2019 at 11:52 AM Corentin <<a href="mailto:corentin.jabot@gmail.com" target="_blank">corentin.jabot@gmail.com</a>> wrote:<br>
><br>
> I suspect it will be a while (several years) before we start to see large projects transitioning fully to modules and consumed as such by tools doing automatic dependency scanning etc.<br>
> My understanding is that there is little large scale implementation experience as far as tooling and build systems are concerned ( there is plenty _compilers_ implementation experience, and some build system implementation (and usage of modules) experience - mostly in build2).<br>
<br>
Given your statement above, why is it useful for SG15 to discuss<br>
enforcing mapping? Specifically, how will that discussion be grounded<br>
in facts? It seems to me like facts need a compiler implementation,<br>
and a codebase to try it out on. Feel free to talk about hypotheticals<br>
all you want, but in this case code wins.<br>
<br>
I think you want to refocus your approach: what are you trying to<br>
achieve? What's the advantage that SG15 has, which the modules SG and<br>
now EWG don't have? How can SG15 contribute module's success?<br>
<br>
<br>
> On Thu, 10 Jan 2019 at 18:47 JF Bastien <<a href="mailto:cxx@jfbastien.com" target="_blank">cxx@jfbastien.com</a>> wrote:<br>
>><br>
>> On Thu, Jan 10, 2019 at 6:53 AM Corentin <<a href="mailto:corentin.jabot@gmail.com" target="_blank">corentin.jabot@gmail.com</a>> wrote:<br>
>> ><br>
>> > Hello.<br>
>> > I would like to suggest two modules related proposals that I think SG15 should look at.<br>
>> ><br>
>> > - Compiler enforced mapping between module names and module interface file (resource) name.<br>
>><br>
>> Why does SG15 need to do this, versus someone implementing it in an<br>
>> open-source toolchain, trying it out, and bringing what using it<br>
>> taught them to SG15?<br>
>><br>
>><br>
>> > Currently, modules interfaces can be declared in any file - which makes dependency scanning more tedious than it needs to be and have performance implications<br>
>> > (The build system needs to open all files to gather a list of modules) - notably when the build system tries to start building while the dependency graph isn't yet complete.<br>
>> ><br>
>> > Tools ( ide, code servers, indexers, refactoring) may also greatly benefit from an easier way to locate the source file which declares a module.<br>
>> ><br>
>> > The specifics of the mapping are open to bikeshedding. However, I think we would have better luck sticking to something simple like <module identifier> <=> <file name>.<extension><br>
>> > (The standardese would mention resource identifier rather than filename)<br>
>> ><br>
>> > - A standing document giving guidelines for modules naming.<br>
>> ><br>
>> > The goal is to take everything the community had to learn the hard way about header naming over the past 30 years and apply it to modules by providing a set of guidelines<br>
>> > that could be partially enforced by build system vendors.<br>
>> > Encouraging consistency and uniqueness of module identifiers across the industry is I think a necessary step towards sane package management.<br>
>> > Note that the standard requires uniqueness of modules identifiers within (the standard definition of) a program but says little about a way to ensure this uniqueness.<br>
>> ><br>
>> > Here is a rough draft of what I think would be good guidelines, partially inspired by what is done by other languages facing similar issues.<br>
>> ><br>
>> > Prefix module names with an entity and/or a project name to prevent modules from different companies, entities and projects of declaring the same module names.<br>
>> > Exported top-level namespaces should have a name identic to the project name used as part of the name of the module(s) from which it is exported.<br>
>> > Do not export multiple top-level namespaces<br>
>> > Do not export entities in the global namespace outside of the global module fragment.<br>
>> > Organize modules hierarchically. For example, if both modules example.foo and example.foo.bar exist as part of the public API of example, example.foo should reexport example.foo.bar<br>
>> > Avoid common names such as util and core for module name prefix and top-level namespace names.<br>
>> > Use lower-case module names<br>
>> > Do not use characters outside of the basic source character set in module name identifiers.<br>
>> ><br>
>> > My hope is that these 2 proposals (whose impact on the standard is minimal) would make it easier for current tooling to deal with modules<br>
>> > while making possible for example to design dependency managers and build systems able to work at the module level.<br>
>> ><br>
>> > I'd love to gather feedback and opinions before going further in that direction.<br>
>> > Thanks a lot!<br>
>> ><br>
>> > Corentin<br>
>> ><br>
>> > PS: For a bit of background, I talked about these issues there<br>
>> ><br>
>> > <a href="https://cor3ntin.github.io/posts/modules_mapping/" rel="noreferrer" target="_blank">https://cor3ntin.github.io/posts/modules_mapping/</a><br>
>> > <a href="https://cor3ntin.github.io/posts/modules_naming/" rel="noreferrer" target="_blank">https://cor3ntin.github.io/posts/modules_naming/</a><br>
>> ><br>
>> ><br>
>> > _______________________________________________<br>
>> > Tooling mailing list<br>
>> > <a href="mailto:Tooling@isocpp.open-std.org" target="_blank">Tooling@isocpp.open-std.org</a><br>
>> > <a href="http://www.open-std.org/mailman/listinfo/tooling" rel="noreferrer" target="_blank">http://www.open-std.org/mailman/listinfo/tooling</a><br>
>> _______________________________________________<br>
>> Tooling mailing list<br>
>> <a href="mailto:Tooling@isocpp.open-std.org" target="_blank">Tooling@isocpp.open-std.org</a><br>
>> <a href="http://www.open-std.org/mailman/listinfo/tooling" rel="noreferrer" target="_blank">http://www.open-std.org/mailman/listinfo/tooling</a><br>
><br>
> _______________________________________________<br>
> Tooling mailing list<br>
> <a href="mailto:Tooling@isocpp.open-std.org" target="_blank">Tooling@isocpp.open-std.org</a><br>
> <a href="http://www.open-std.org/mailman/listinfo/tooling" rel="noreferrer" target="_blank">http://www.open-std.org/mailman/listinfo/tooling</a><br>
_______________________________________________<br>
Tooling mailing list<br>
<a href="mailto:Tooling@isocpp.open-std.org" target="_blank">Tooling@isocpp.open-std.org</a><br>
<a href="http://www.open-std.org/mailman/listinfo/tooling" rel="noreferrer" target="_blank">http://www.open-std.org/mailman/listinfo/tooling</a><br>
</blockquote></div></div>