[cfe-dev] [Clang-tidy] Detecting if a catch was done by const ref

[Aaron Ballman via cfe-dev]

On Mon, Mar 12, 2018 at 4:49 PM, Matthieu Brucher via cfe-dev
<cfe-dev at lists.llvm.org> wrote:
>
>
> 2018-03-12 19:39 GMT+00:00 Aaron Ballman via cfe-dev
> <cfe-dev at lists.llvm.org>:
>>
>> On Mon, Mar 12, 2018 at 3:34 PM, Richard via cfe-dev
>> <cfe-dev at lists.llvm.org> wrote:
>> > [Please reply *only* to the list and do not include my email directly
>> > in the To: or Cc: of your reply; otherwise I will not see your reply.
>> > Thanks.]
>> >
>> > In article
>> > <CAAt6xTvjSPEg7OVPWVbtqWdsDp5zja9_TfLTkdzoNoksmEr=KQ at mail.gmail.com>,
>> >     Aaron Ballman via cfe-dev <cfe-dev at lists.llvm.org> writes:
>> >
>> >> I believe the matcher you're looking for is:
>> >> varDecl(hasType(references(qualType(isConstQualified()))))
>> >>
>> >> For example, given:
>> >>
>> >> void f1() {
>> >>   try {
>> >>   } catch (int &e) {
>> >>   }
>> >> }
>> >>
>> >> void f2() {
>> >>   try {
>> >>   } catch (const int &e) {
>> >>   }
>> >> }
>> >>
>> >> produces:
>> >>
>> >> clang-query> match
>> >> varDecl(hasType(references(qualType(isConstQualified()))))
>> >>
>> >> Match #1:
>> >>
>> >> C:\Users\Aaron\Desktop\test.cpp:9:12: note: "root" binds here
>> >>   } catch (const int &e) {
>> >>            ^~~~~~~~~~~~
>> >> 1 match.
>> >
>> > I think they want to match the catches that aren't const qualified, so
>> > it might be (untested):
>> >
>> > varDecl(hasType(references(qualType(not(isConstQualified())))))
>>
>> Ah, oops, I didn't see that I had the predicate reversed. Your matcher
>> is close, but instead of not(), you use unless().
>>
>> ~Aaron
>>
>> > --
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>
>
> Excellent! I thought I had to use the catch statement, but this is indeed
> far better.
> I guess you have to know the AST matcher expressions... Are there tutorials
> on top of the doxygen doc? Or perhaps even books?

There aren't any books that I'm aware of, and I'm not certain about
other tutorials (perhaps they exist and I've simply not found them). I
mostly go off the AST dumps (clang -cc1 -ast-dump foo.cpp), the AST
matchers reference, clang-query, and trial & error.

~Aaron

>
> Regards,
>
> Matthieu
> --
> Quantitative analyst, Ph.D.
> Blog: http://blog.audio-tk.com/
> LinkedIn: http://www.linkedin.com/in/matthieubrucher
>
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