[LLVMdev] RFC: variable names

[Philip Reames]

On 10/13/2014 05:23 PM, Sean Silva wrote:
>
>
> On Mon, Oct 13, 2014 at 5:09 PM, Jim Grosbach <grosbach at apple.com 
> <mailto:grosbach at apple.com>> wrote:
>
>
>>     On Oct 13, 2014, at 4:31 PM, Chandler Carruth
>>     <chandlerc at google.com <mailto:chandlerc at google.com>> wrote:
>>
>>
>>     On Mon, Oct 13, 2014 at 4:14 PM, Chandler Carruth
>>     <chandlerc at google.com <mailto:chandlerc at google.com>> wrote:
>>
>>             1. Initialisms. It's common in Clang code (also in LLVM?)
>>             to use initialisms as variable names. This doesn't really
>>             seem to work for names that start with a lower case letter.
>>
>>
>>         I think wee at least need a good answer to this.
>>
>>
>>     As I really suspect this is the most important point to address,
>>     let me make an attempt:
>>
>>     Variable names are *either* initialisms, written as all caps, or
>>     terms written in lower case and separated by underscores. For the
>>     purposes of variable naming "terms" can include words but also
>>     extremely common and recognizable abbreviations within LLVM such
>>     as "rhs", "lhs", or "gep". These types of terms should not be
>>     written as initialisms but as words. For example, you might write
>>     "LE" or "lhs_expr" for the Left-hand Expression, but not "LHSE"
>>     or "LHS_expr".
>>
>>     While I'm trying to avoid it, this has the advantage of leaving a
>>     large number of initialisms in the existing code base as "stylish".
>>
>>
>>     I'm not really happy with this rule, but it is the least
>>     disruptive and most consistent I can come up with. I would also
>>     be happy encouraging people to not use initialisms excessively or
>>     if confusing. I think the current codebase uses them more than is
>>     helpful.
>
>     This makes sense to me. I think it strikes a good balance between
>     updating our conventions to be better and also reflecting common
>     in-practice usage patterns.
>
>
> This convention sounds like it would cause people to have to be 
> constantly asking themselves "is this common enough to be an 
> initialism-as-word or not?". The thing that started this conversation 
> was someone complaining about going between codebases that they 
> weren't sure whether to capitalize; now that person will have to get a 
> feel for the local initialism-as-word's, which is a much greater 
> burden than just the naming convention.
>
> -- Sean Silva
In practice, you have to set such a threshold somewhere.  Otherwise, you 
end up not being able to use terms like SSA, or Phi without an 
explanation.  My view is that common initialisms like lhs, gep, and dt 
should be accepted.  If you haven't spent enough time in the code to 
recognize them, you probably shouldn't have commit rights anyways.

I am in favor of keeping that list of initialisms small.  Adding a new 
one (either for an area, or the project as a whole) should trigger 
discussion outside of a single review thread.

Philip
>
>
>>     FWIW, I think that having different naming conventions for data
>>     members and local variables has become essentially untenable with
>>     lambdas and capture.
>
>     Can you elaborate a bit more on this? Maybe an example or two.
>
>     I’m very supportive of the general direction of all of this. Glad
>     to see the general consensus developing.
>
>     -Jim
>
>
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