[PATCH] D122895: [C89/C2x] Improve diagnostics around strict prototypes in C

Aaron Ballman via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Fri May 13 12:09:32 PDT 2022


aaron.ballman added a comment.

In D122895#3512341 <https://reviews.llvm.org/D122895#3512341>, @aaron.ballman wrote:

> I think the current behavior today makes sense but we should see if we can improve it to make *more* sense. With `-Wstrict-prototypes`, we should complain about the block without a prototype, but the use at the call site is not declaring a conflicting declaration nor is it a call to a function without a prototype but passes arguments (both of those are `-Wdeprecated-non-prototype` warnings). Instead, it's a new kind of situation that we may want to consider adding additional coverage for under `-Wdeprecated-non-prototype` based on the same reasoning we used for diagnosing calls to a function without a prototype but pass arguments. This is not specific to blocks, consider:
>
>   void func(void (*fp)());
>   void do_it(int i);
>   
>   int main(void) {
>     func(do_it); // It'd be nice to diagnose this too, but we don't today
>   }

Mostly as a note to myself (but others can definitely chime in if they think I'm wrong here), I *think* the correct way to handle both blocks and function pointers is to add new `AssignConvertType` enumerators for `IncompatibleC2xFunctionPointer` and `IncompatibleC2xBlockPointer` to represent an assignment conversion that is compatible today but will be incompatible in C2x. Then functions like `checkPointerTypesForAssignment()` and `checkBlockPointerTypesForAssignment()` can return the new value, which `DiagnoseAssignmentResult()` can use to determine whether to diagnose a potential behavior change or not.


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https://reviews.llvm.org/D122895



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