[cfe-dev] Diagnostic won't emit

[Andrzej Warzynski via cfe-dev]

Can you check the DiagnosticConsumer in your example? AFAIK, 
TextDiagnosticBuffer will not print the diagnostics unless they are 
flushed. By default, the compiler driver (e.g. clang) creates 
TextDiagnosticPrinter and that's what you want to use. In a standalone 
example you are the one implementing the driver and _you_ need to make 
sure that your DiagnosticConsumer does what you expect :)

As for the examples in clang-tutor, those are mostly dynamically loaded 
plugins. Here's how you can run the one that I pointed you to (you can 
also check the RUN command in the test that I referred to):

```
bin/clang -cc1  -load 
<clang-tutor-build-dir>/lib/libCodeStyleChecker.dylib -plugin 
code-style-checker -fcolor-diagnostics 
<clang-tutor-dir>/test/CodeStyleCheckerMacro.cpp
```

As this is a dynamically loaded plugin, there's no `main` (more 
specifically - clang's `main` drives this).

If you prefer a stand-alone example that implements `main`:
* 
https://github.com/banach-space/clang-tutor/blob/67df06ba2474e6e08d828692cf7d4f0f7374b16e/tools/LACommenterMain.cpp#L50-L57

You will notice that I don't have a stand-alone tool that runs 
CodeStyleChecker. I can experiment with that and upload it. Or, if 
you're quicker than me, you can submit a patch on GitHub!

-Andrzej

On 10/10/2020 12:05, Billy O'Mahony wrote:
> The code in those the CodeSytleChecker example looks  more or less 
> identical to my code above, so it must be something to do with setting 
> up a DiagnosticConsumer or overriding  a method somewhere in a derived 
> class.
> 
> Thanks for maintaining those examples - they look really useful - I 
> wish I'd seen them sooner :)
> 
> I'll download them and see if I can get them to run. Where is main() for 
> the CodeCheckerApp by the way - it's not in CodeChecker.cpp?
> 
> On Fri, 9 Oct 2020 at 20:43, Billy O'Mahony <billy.omahony at gmail.com 
> <mailto:billy.omahony at gmail.com>> wrote:
> 
>     Hi Andrzej,
> 
>     thanks for the reply. My code is basically identical to the mccabe
>     example:
> 
>     454             const clang::BinaryOperator *binOp =
>     parents[0].get<clang::BinaryOperator>();
>     455             if (!binOp || binOp->getOpcodeStr() !=
>     std::string("="))  // TODO check for isAssignmentOp
>     456             {
>     457                 auto& Diagnostics = mContext->getDiagnostics();
>     458                 const auto ID =
>     Diagnostics.getCustomDiagID(clang::DiagnosticsEngine::Error,
>     459                                                            
>     "Return value from '%0' is not assigned");
>     460                 auto Builder =
>     Diagnostics.Report(fnDecl->getLocation(), ID);
>     461                 Builder.AddString(fnDecl->getNameAsString());
>     462
>     463                 cout << "ERROR: Return val from API call not
>     assigned '" << Diagnostics.getClient() << " " <<
>     fnDecl->getNameAsString()
>     464                 return true;
>     465             }
> 
>     I know that my DiagnosticsEngine does have a DiagnosticConsumer as
>     Diagnostics.getClient() returns non-null.
> 
>     My understanding is that when the Build object is destroyed after
>     the return that the diagnostic should be emitted.
> 
>     I will have a look at those samples.
> 
>     Thanks,
>     Billy.
> 
>     On Fri, 9 Oct 2020 at 20:18, Andrzej Warzynski
>     <andrzej.warzynski at arm.com <mailto:andrzej.warzynski at arm.com>> wrote:
> 
>         Hi Billy,
> 
>         It's a bit tricky to help without seeing the code :) Are you
>         using any
>         specific/custom diagnostic consumer? Is your properly
>         DiagnosticBuilder
>         destroyed? AFAIK, that's when the message is printed.
> 
>         Here's a bit more up-to-date example:
>         *
>         https://github.com/banach-space/clang-tutor/blob/master/lib/CodeStyleChecker.cpp#L97-L102
>         And a test that verifies that the diagnostic is indeed printed:
>         *
>         https://github.com/banach-space/clang-tutor/blob/master/test/CodeStyleCheckerMacro.cpp
> 
>         Happy to help if that example doesn't work for you! Hopefully it
>         will
>         help debugging your own code :)
> 
>         -Andrzej
> 
>         On 09/10/2020 16:26, Billy O'Mahony via cfe-dev wrote:
>          > Hi,
>          >
>          > hopefully a straightforward issue.
>          >
>          > I have written a standalone cfe tool to catch some
>         project-specific bugs
>          > in a code base.
>          >
>          > I am now replacing my cout << "ERROR..." messages with
>          > clang::Diagnostics by following this example:
>          >
>          >
>         https://github.com/peter-can-talk/cppnow-2017/blob/master/code/mccabe/mccabe.cpp#L46-L54
>          >
>          > However I don't see anything being printed when I run it
>         (except my own
>          > cout << "error.." messages)..
>          >
>          > I've seen the mcabbe example generate diagnostics on a
>          > youtube presentation and both it and my app use
>          > clang::Tool.  mccabbe uses ast_matcher::MatchFinder whereas I
>         use
>          > several classes derived from RecursiveASTVisitor. Presumably
>         MatchFinder
>          > sets up a DiagnosticsConsumer that finally emits the
>         diagnostics??
>          >
>          > But I couldn't really find out how to set up a
>         DiagnosticsConsumer - if
>          > that is indeed what I need to do.
>          >
>          > Thanks,
>          > Billy.
>          >
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