[llvm] r301152 - [Orc] Fix a warning by removing an unused lambda capture.

[David Blaikie via llvm-commits]

On Sat, May 6, 2017 at 10:52 AM Lang Hames <lhames at gmail.com> wrote:

> I think of such lambdas as basically programmatic control flow (like an
>> if, while, etc) - so there's no need to explicitly state which variables
>> you'll use within this nested scope.
>
>
> Good idea.
>
> This is probably too heavyweight to do as a warning, but some sort of
> style-checker plugin could suggest using default capture for non-escaping
> lambdas and explicit capture for may-escape ones.
>

Yeah, pretty tricky to do, though - for example this use case would
probably fall into the "may escape" case (since it's passed to another
function which might then capture it into a std::function for later use,
etc). Essentially only local lambdas called directly (not used by passing
to any algorithm-like functions, etc) would be "doesn't escape". (or you
could conservatively assume that anywhere you don't see the lambda copied
to a std::function ctor is fine? Though that might aggressively encourage
default capture where it shouldn't be, etc)

Tricky one, I suspect,
- Dave


>
> - Lang.
>
> On Mon, Apr 24, 2017 at 9:13 AM, David Blaikie <dblaikie at gmail.com> wrote:
>
>> Generally if a lambda's only going to be used within its own scope - I'd
>> suggest using [&]. I think of such lambdas as basically programmatic
>> control flow (like an if, while, etc) - so there's no need to explicitly
>> state which variables you'll use within this nested scope.
>>
>> On Sun, Apr 23, 2017 at 6:34 PM Lang Hames via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: lhames
>>> Date: Sun Apr 23 20:21:23 2017
>>> New Revision: 301152
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=301152&view=rev
>>> Log:
>>> [Orc] Fix a warning by removing an unused lambda capture.
>>>
>>> Modified:
>>>     llvm/trunk/include/llvm/ExecutionEngine/Orc/RPCSerialization.h
>>>
>>> Modified: llvm/trunk/include/llvm/ExecutionEngine/Orc/RPCSerialization.h
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ExecutionEngine/Orc/RPCSerialization.h?rev=301152&r1=301151&r2=301152&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/include/llvm/ExecutionEngine/Orc/RPCSerialization.h
>>> (original)
>>> +++ llvm/trunk/include/llvm/ExecutionEngine/Orc/RPCSerialization.h Sun
>>> Apr 23 20:21:23 2017
>>> @@ -378,7 +378,7 @@ public:
>>>        return serializeSeq(C, std::string());
>>>
>>>      return handleErrors(std::move(Err),
>>> -                        [&C, &Lock](const ErrorInfoBase &EIB) {
>>> +                        [&C](const ErrorInfoBase &EIB) {
>>>                            auto SI =
>>> Serializers.find(EIB.dynamicClassID());
>>>                            if (SI == Serializers.end())
>>>                              return serializeAsStringError(C, EIB);
>>>
>>>
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>>
>
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