[LLVMdev] Any objections to turning on -Wunused-parameter? (and any other -Wunused-* that are off?)

[Chandler Carruth]

LLVM has a separate flag for making warnings errors, and I'm not proposing
to change this settings default.

I'm satisfied with the fact that when submitted, a patch is expected to be
free of warnings.

On Mon, Jul 20, 2015 at 4:52 PM David Blaikie <dblaikie at gmail.com> wrote:

> On Mon, Jul 20, 2015 at 4:18 PM, Philip Reames <listmail at philipreames.com>
> wrote:
>
>>  I'd be very happy to see this turned on as a warning; I'd be very
>> reluctant to see it turned on as a error.  During a lot of code cleanups,
>> the intermediate state of "deleted, but dead args still passed in" is a
>> very useful intermediate step.  It greatly simplifies review to be able to
>> separate the meat of the semantic change from the "just deleting a bunch of
>> dead args" patch.  I'd be very very reluctant to create a situation where
>> the patch with the semantic change but without the argument cleanup won't
>> pass all the build bots.
>>
>
> Yep - I recall Chandler expressing similar consternation when he & I have
> discussed -Wunreachable-code so I was a bit surprised to see the suggestion.
>
> But that said, in this case it doesn't seem too costly to comment out the
> name of the parameter in the first patch - it is an extra change, but
> doesn't require touching all the callers, etc. Then do the removal in a
> follow up patch still.
>
>
>>
>> Philip
>>
>> (1 inline comment below as well)
>>
>> On 07/18/2015 02:48 AM, Chandler Carruth wrote:
>>
>> LLVM and Clang both have lots of objects that are passed through many
>> different API boundaries. Things like AliasAnalysis in LLVM or Sema in
>> Clang get threaded all over the place.
>>
>>  Over times, refactoring can often cause the parameters (or local
>> variables, or member variables, etc) to become dead. If we notice this, we
>> can often un-thread the interface through our APIs, sometimes even reducing
>> coupling, etc.
>>
>>  But currently -Wunused-parameter is hard disabled. I've not checked to
>> see if there are any other disabling of -Wunused-* variants, but I'd like
>> to move the project toward firmly enabling them and being clean with them.
>>
>>  The technique I'd like to use is leaving out names of unused
>> parameters, using a /*CommentedName*/ if there is a useful name, otherwise
>> just omitting the name.
>>
>> Sorry, could you rephrase?  Not sure what you're getting at here.
>>
>>
>>  All of this will require a reasonable amount of cleanup across the
>> projects which I'm happy to do prior to flipping defaults around. Thoughts?
>> Any concerns or objections?
>>
>>  (I'll ask the same question and ofter to either enact the cleanups or
>> toggle the warning(s) back off for each of the less intertwined subprojects
>> like LLD, LLDB, Polly, etc.)
>>
>>  -Chandler
>>
>>
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