[cfe-dev] [Modules TS] Have the file formats been decided?

[Stephen Kelly via cfe-dev]

Sean Silva via cfe-dev wrote:

>> I don't know what the 'developer
>> story' is apart from 'wait for all of your dependencies to update with
>> modules support and wait for each buildsystem of your dependency to be
>> compatible with all the others for creating and consuming modules and
>> then you can start using modules'.
> 
> The problem for C++ modules is actually worse than just "wait for your
> dependencies". You also may need to wait for your dependents since the
> modules syntax is incompatible with pre-modules compilers (though last I
> talked with Richard about this he had some pretty clear ideas for keeping
> the overhead down during the transition period, which for some projects
> will be "forever").

I would be interested to hear more from Richard about this.

> Waiting for your dependencies and dependents is a bit of a catch-22
> unfortunately; we just need to hope that intermediate transitionary steps
> are available to break the deadlock.

That does sound like a problem.

> Between different build systems, package managers, etc. the deadlock is
> even stronger (nobody wants to take the first step because nobody's first
> step adds any value without the others).

I'm not certain what you're referring to. Perhaps what you have in mind is 
some standardization/conventions for buildsystems. I doubt that's possible. 
I think it would be better if Modules were designed to not have that impact.

>> I realize this goes beyond Clang and the ModulesTS has buildsystem issues
>> too...
>>
> 
> One interesting point here is that it's clear that some sort of
> standardization is going to be needed "outside the ISO C++ Standard" (e.g.
> conventions for build systems etc.). 

I can't imagine how anyone would get something like that started.

> It may be too early for that work to
> start, 

I don't agree with that. I think the design of C++ Modules and the impact 
the design has on buildsystems are coupled. A brilliantly designed Modules 
system which does not consider the buildsystem (or the impact on how people 
write code - what files they write and how they relate to each other in the 
way that .h and .cpp files do today etc) might not get the deserved 
adoption.

> but I haven't seen much on that front (though admittedly I'm not
> actively following all this modules stuff in detail anymore). If you're in
> a position where you can contribute to that effort it would be *hugely*
> appreciated I'm sure!

I'm not sure how appreciated it will be, but I have attempted to ask some 
starting questions here:

 https://groups.google.com/a/isocpp.org/forum/?fromgroups#!topic/modules/sDIYoU8Uljw

Those are not all the questions I have, but you are correct that the 
conversation about the impact of Modules on buildsystems does not currently 
exist at all, so starting smaller is better.

Thanks,

Steve.