[cfe-dev] Implementing -Wunused-variables

[Oscar Bonilla]

On Oct 6, 2009, at 9:12 AM, Oscar Bonilla wrote:

> On Oct 5, 2009, at 11:37 PM, Oscar Bonilla wrote:
>
>> On Oct 5, 2009, at 9:46 PM, Oscar Bonilla wrote:
>>
>>> Is this any better?
>>
>> Still not quite right:
>
> Ok, this one seems to do the trick:
>
> <ob.patch>
>
> Testcases:
>
> <warn-unused-variables.c><warn-unused-variables.cpp>
>
> I ran "make test" and only got one failure:
>
> FAIL: Clang::Index/c-index-api-test.m (646 of 1636)
>
> which seems unrelated. I also compiled Adium with it and didn't get  
> any obvious false positives or false negatives.
>

Would it be better to write the if in SemaDecl.cpp

     if (isa<VarDecl>(D) && !isa<ParmVarDecl>(D) && ! 
isa<ImplicitParamDecl>(D) &&
	D->getDeclContext()->isFunctionOrMethod() &&
	!D->isUsed() && !D->hasAttr<UnusedAttr>()) {
	    Diag(D->getLocation(), diag::warn_unused_variable) << D- 
 >getDeclName();
     }

as

     if (!D->isUsed() && !D->hasAttr<UnusedAttr>() &&
	isa<VarDecl>(D) && !isa<ParmVarDecl>(D) && !isa<ImplicitParamDecl>(D)  
&&
	D->getDeclContext()->isFunctionOrMethod()) {
	    Diag(D->getLocation(), diag::warn_unused_variable) << D- 
 >getDeclName();
     }

i.e. move the "not used and no unused attr" to the beginning to take  
advantage of short-circuit logic?

or is this kind of micro-optimizing frowned upon? :)

Cheers,

-Oscar