[PATCH] D128328: [C++20][Modules] Improve handing of Private Module Fragment diagnostics.

Chuanqi Xu via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Thu Jun 23 00:43:14 PDT 2022

ChuanqiXu added a comment.

In D128328#3603945 <https://reviews.llvm.org/D128328#3603945>, @iains wrote:

> In D128328#3603942 <https://reviews.llvm.org/D128328#3603942>, @ChuanqiXu wrote:
>> In D128328#3603940 <https://reviews.llvm.org/D128328#3603940>, @iains wrote:
>>> In D128328#3602646 <https://reviews.llvm.org/D128328#3602646>, @iains wrote:
>>>> In D128328#3601080 <https://reviews.llvm.org/D128328#3601080>, @ChuanqiXu wrote:
>>>>> It looks like we need to handle inline variable as well to match the intention.
>>>> can you construct a test-case, where this would apply and which is not already diagnosed as incorrect?
>>> Did you have some ideas here?
>> The test may be something like:
>>   export module A;
>>   inline int a;
>>   module :private
>>   int a = 0; // expected-error 
> but we reject this at the moment with "redefinition of 'a'" - so that implies we do not have fully correct C++17 handling here?

Sorry, my bad. The configuration of my godbolt was wrong (The input is LLVM IR). I feel like the following one should be the test case:

  export module A;
  [export] inline int a;

Here the inline variable 'a' is declared in the definition domain but not defined. This violates [dcl.inline]p7:

> If an inline function or variable that is attached to a named module is declared in a definition domain, it shall be defined in that domain.

Also, **if** [module.private.frag]p2.1 is changed into:

> the point by which the definition of an [exported] inline function or variable is required

The test above would test this too.

BTW, it shows we could lack test like:

  export module A;
  [export] inline void func(); // no definition in the definition domain

The meaning of [export] depends on the result of the feedback from WG21.

>> But I feel like we couldn't  go on before we get response from WG21.
> Agreed, and anyway I think we would want to add a new test case, not to amend the example from the std (otherwise that becomes confusing as well)

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