[cfe-dev] Writing a fix-it for errors already found by clang

[Jonas Toth via cfe-dev]

Hi Stuart,

I am not too active in the frontend, but in `lib/Parse/*` is the code
for parsing and it does emit FixitHints. You can grep around with

`git grep "FixItHint::CreateInsertion"`

Documentation for FixIt:
https://clang.llvm.org/doxygen/classclang_1_1FixItHint.html

Documentation for CFE Internals:
https://clang.llvm.org/docs/InternalsManual.html#fix-it-hints

Someone else might give you more specific advice, but reading the code
and some doc might give you a good start :)

Best Jonas


Am 05.10.2018 um 12:50 schrieb Stuart Thomson:
>
> Hi Jonas,
>
>  
>
> Thanks for this.
>
>  
>
>   * As far as I can tell clang does not emit a fix-it hint for this
>     error. There is no hint on the command line and running clang-tidy
>     with -fix-errors results in no change in the source.
>   * Dumping the AST shows the VarDecl in question but it is marked
>     “invalid”. Also when I try to write a matcher it doesn’t seem to
>     be able to find the initializer so I think you are right that the
>     node has been removed.
>
>  
>
> I’m not sure how exactly I would go about adding this to the frontend
> – do you have any suggestions for how to begin?
>
>  
>
> Cheers,
>
> Stuart
>
>  
>
>  
>
> *From:*Jonas Toth <development at jonas-toth.eu>
> *Sent:* 05 October 2018 11:05
> *To:* Stuart Thomson <Stuart.Thomson at eu.medical.canon>;
> cfe-dev at lists.llvm.org
> *Subject:* Re: [cfe-dev] Writing a fix-it for errors already found by
> clang
>
>  
>
> Hi Stuart,
>
> does clang itself emit a fix-it hint? As it does for some errors
> already, you could try to add this to the clang frontend itself
> instead of a separate clang-tidy check.
>
> clang-tidy checks don't have information of other diagnostics from
> Sema or other checks, each check is independent in that sense. They
> use the AST as information.
> When there are errors in the original source-code, the corresponding
> AST-Nodes could be removed to recover from these errors. This makes it
> complicated to write
> a reliable clang-tidy check (if not impossible).
>
> Does 'clang-check -ast-dump file.cpp' contain the offending nodes?
>
> Best Jonas
> (forgot to include cfe-dev)
>
> Am 05.10.2018 um 11:56 schrieb Stuart Thomson via cfe-dev:
>
>     Hi,
>
>      
>
>     I want to write a clang-tidy check which would fix something which
>     clang currently considers an error (namely initializing BSTR with
>     const wchar_t *). I am trying to write node matchers etc. but it
>     seems like it might be redundant given that clang already know
>     when this is happening. I wonder if there is some way to grab the
>     diagnostic messages and if the message matches a given message
>     (with a regex or something) clang could attempt to fix the
>     offending code?
>
>      
>
>     Also, is this complicated by the fact that this diagnostic is and
>     error and not just a warning?
>
>      
>
>     Thanks,
>
>     Stuart
>
>      
>
>      
>
>
>
>
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