From:  Lars Hansen <lhansen@mozilla.com>
Date:  29 Sep 2017 17:43:55 Hong Kong Time
Newsgroup:  news.mozilla.org/mozilla.dev.tech.js-engine.internals
Subject:  

Re: C++ coding style rule for keeping class fields together

NNTP-Posting-Host:  63.245.214.181

On Thu, Sep 28, 2017 at 9:35 PM, Jason Orendorff 
wrote:

> On Thu, Sep 28, 2017 at 2:10 AM, Lars Hansen  wrote:
>
>> I dislike this proposal.  (a) A lot of the code I work with already have
>> fields-at-the-beginning as the predominant pattern in the smaller classes
>> (jit, wasm) so this would be major churn for no gain.  (b) For large
>> classes this is an anti-pattern, like having all the vars at the beginning
>> of a function in C; it separates the data from the functions that work on
>> that data.  (c)  It brings private and public parts of the code close
>> together, and separates public data from public methods.
>>
>
> Objections (a) and (b) make sense to me, so let's make the rule "For
> reasonable-sized classes, put all the fields together, at the top
> (immediately after any necessary typedefs). For unreasonably large classes,
> do whatever seems best (but let's try to avoid making more of these)."
> Better?
>

​Much better.
​

>
> I don't really understand objection (c); maybe an example from SM code
> would clear it up. (But let me grant in advance that all style rules are
> subordinate to George Orwell's sixth rule: "Break any of these rules sooner
> than say anything outright barbarous.")
>

​I admit this is a more generic concern.  When I write code that is part of
a module API I like to separate the public bits from the private bits and I
usually do this textually (public members and methods at the top; private
at the bottom) since C++ pretty much forces me to add the private bits to
the publically visible class definition unless I want to jump through a lot
of hoops to hide them and pay the cost of virtual methods.

--lars
​, still misses Modula-3's partial revelations​
​

>
> -j
>
>