[cfe-dev] Implementing -Wunused-variables

[Oscar Bonilla]

On Oct 5, 2009, at 7:54 AM, Douglas Gregor wrote:

> Generally, the best way to figure out how to add a new warning like  
> this is to find a similar warning. Clang has -Wunused-parameter  
> already implemented, so that's a great start. There are a few places  
> you'll need to look at and (in some cases) modify to implement - 
> Wunused-variables:
>
> 	include/clang/Basic/DiagnosticSemaKinds.td: define a new  
> warn_unused_variable warning here
> 	lib/Sema/Sema.h: DiagnoseUnusedParameters shows how to emit a  
> similar warning
> 	lib/Sema/SemaDecl.cpp: Sema::ActOnPopScope is where you probably  
> want to look for unused variables (when they are being popped out of  
> scope)
>   	lib/Sema/SemaExpr.cpp: Sema::MarkDeclarationReferenced is called  
> whenever any declaration (variable, function, method, etc.) is used  
> by the source code.
>
> Most of the documentation for the ASTs is within the AST headers,  
> which is also accessible via Doxygen:
>
> 	http://clang.llvm.org/doxygen/
>
> 	- Doug

Okay, this seems to do it:

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and here's the testcase (I put it in test/Sema/warn-unused-variables.c

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Let me know if I did it right ;)

Cheers,

-Oscar