[PATCH] Add a level parameter to ClangTidyCheck::diag.

[Alp Toker]

On 03/03/2014 12:53, Alexander Kornienko wrote:
> On Sun, Mar 2, 2014 at 5:59 PM, Alp Toker <alp at nuanti.com 
> <mailto:alp at nuanti.com>> wrote:
>
>
>     On 02/03/2014 16:18, Alp Toker wrote:
>
>
>         On 02/03/2014 12:25, Peter Collingbourne wrote:
>
>
>             Index: clang-tidy/ClangTidy.h
>             ===================================================================
>             --- clang-tidy/ClangTidy.h
>             +++ clang-tidy/ClangTidy.h
>             @@ -76,7 +76,8 @@
>                 void setContext(ClangTidyContext *Ctx) { Context = Ctx; }
>                   /// \brief Add a diagnostic with the check's name.
>             -  DiagnosticBuilder diag(SourceLocation Loc, StringRef
>             Description);
>             +  DiagnosticBuilder diag(SourceLocation Loc, StringRef
>             Description,
>             +                         DiagnosticIDs::Level Level =
>             DiagnosticIDs::Warning);
>
>
>         Could you order the parameters Loc, Level, FormatString and
>         drop the default argument?
>
>         That'll provide visual consistency with the output as well as
>         internal consistency with clang's own getCustomDiagID(Level L,
>         StringRef FormatString).
>
>         That way it becomes kind of a shorthand for
>         diag(getCustomDiagID(...)) << ... which is a step towards
>         unifying built-in and custom diagnostic IDs.
>
>
>     So it looks like there's a convention of listing the diag Level
>     _after_ the Message clang-tools-extra, and diag(Loc, "message")
>     without specifying a Level. Neither looks like a good idea but if
>     the plan is to keep that convention then I guess your patch is OK.
>
>     It's a failing of clang's diag/tablegen system that it wasn't made
>     reusable and ended up getting re-rolled in external projects, each
>     with slightly different interfaces :-/
>
>
> Yes, there's a lot to unify and clean up in this area. If we can come 
> up with a proper interface to manage diagnostic ID spaces, so that 
> tablegen'd diagnostic tables can be registered dynamically, I'd be 
> happy to clean up clang-tidy and static analyzer to use this system.

Right on.
>
> In the simplest case, we'd need some analogues for struct 
> StaticDiagInfoRec and maybe struct StaticDiagCategoryRec and a method 
> to register a block of them and return the diagnostic ID of the first 
> element, so that the client code could use it as an offset to the 
> local static IDs.

Agree, but with one significant distinction: It's those "analogues" that 
created this problem in the first place where we have essentially two 
parallel diagnostic systems in clang plus another one currently being 
developed in LLVM core.

We really need to peel things back at this point so structures like 
StaticDiag*Rec are shared by built-in and custom diagnostic code paths 
instead of duplicated. They're generic descriptions after all so it 
might be as straightforward as moving them out of the cpp to a .h file 
and taking it from there. Ditto getting diag td files to include 
"Diagnostic.td" instead of the reverse that exists now -- otherwise 
maintaining out-of-tree diagnostic tds is a non-started.

As for registering blocks of diagnostic IDs, that's been kind of 
unpleasant and doesn't scale well to plugins and external projects. My 
early thought here is to represent diagnostic IDs as a 32-bit hash of 
the Rec contents that'll be computed by TableGen at compile time, as 
well as optionally at runtime for diagnostics that need to be defined 
dynamically. Should solve various quirks that are getting swept under 
the carpet today.

>
> What do you think about this?

Keen to go ahead with it so long as we're treating the work as 
much-needed cleanup, with clang-tools-extra getting the functionality 
when it's ready. It is a non-trivial but the reduction in cruft and will 
surely pay off.

Alp.

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