r250577 - [modules] Allow the error when explicitly loading an incompatible module file

[Manuel Klimek via cfe-commits]

On Tue, Oct 20, 2015 at 11:11 PM Sean Silva <chisophugis at gmail.com> wrote:

> On Tue, Oct 20, 2015 at 6:45 AM, Manuel Klimek <klimek at google.com> wrote:
>
>> On Tue, Oct 20, 2015 at 3:38 PM Brad King <brad.king at kitware.com> wrote:
>>
>>> On 10/20/2015 04:38 AM, Manuel Klimek wrote:
>>> > On Tue, Oct 20, 2015 at 5:52 AM Sean Silva wrote:
>>> >> get cmake to generate clang module map files and add explicit module
>>> build steps?
>>> >
>>> > I have some experience hacking on cmake, and from my experience I think
>>> > this shouldn't be too hard to get working (mainly work ;)
>>>
>>> I agree this shouldn't be too hard on the CMake side.  Manuel, please
>>> come over to the cmake dev list to raise the design discussion.  Then
>>> we can guide your implementation work.
>>
>>
>> I think Sean volunteered :) (but please keep me cc'ed if you start
>> discussing this on cmake-dev)
>>
>>
>>>   The main design challenges
>>> I foresee are:
>>>
>>> 1. Deciding how this behavior should be activated for a project by
>>>    its code and/or by the user.
>>>
>>> 2. Selection of the proper set of headers if it is not exactly the set
>>>    listed in the target for some reason.  Might this ever by more
>>>    granular than a whole library target?
>>>
>>
>> I don't think so.
>> Main concerns are:
>> 1. we need to be able to say something is a "textual" header; those are
>> still needed; we can do that by calling them .inc, or by putting something
>> into cmake to specify textual headers (that's what we do in our build
>> system)
>> 2. for the "slow rollout" case we use per-header submodules; but that's
>> more an implementation detail than anything else, I think
>>
>
> What is the "slow rollout" case?
>

The case where you want to migrate parts of the codebase to modules, while
other parts are not touched (and you don't necessarily want to do a full
bottom-up modularization).

"slow" as opposed to "one big swoop"


>
> -- Sean Silva
>
>
>>
>>
>>>
>>> 3. Finding the right place during the CMake generation process to add
>>>    the rules for this.
>>>
>>> We already detect the Clang compiler version so deciding if it is
>>> new enough to support the feature should not be hard.
>>>
>>> Thanks,
>>> -Brad
>>>
>>>
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