[LLVMdev] RFC: variable names (original) (raw)

Sean Silva chisophugis at gmail.com
Mon Oct 13 17:56:41 PDT 2014

On Mon, Oct 13, 2014 at 5:46 PM, Philip Reames <listmail at philipreames.com> wrote:

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> wrote:

On Oct 13, 2014, at 4:31 PM, Chandler Carruth <chandlerc at google.com> wrote:

On Mon, Oct 13, 2014 at 4:14 PM, Chandler Carruth <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 "lhsexpr" for the Left-hand Expression, but not "LHSE" or "LHSexpr". 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.

FWIW I don't know what dt means here (dominator tree? debug type?)

Remember, one of the gripes about the current convention is that it is a turn-off for people new to LLVM development (which often means not that knowledgable about compilers). Thus "you probably shouldn't have commit rights anyways" is an extremely counter-productive way to think about this.

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.

This sounds like a strict increase in the amount of thinking about pointless things that I have to do when coming up with a variable name. Currently I only have to think about where my current file is. Now you are suggesting that I should have to think about whether something is common enough or not (which is actually real "AI Complete" thinking)?

-- Sean Silva

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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