From:  Nicholas Nethercote <>
Date:  29 Sep 2017 08:51:36 Hong Kong Time

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


I sometimes want to know the memory layout of a class/struct. Having all
the fields together makes that a *lot* easier.


On Fri, Sep 29, 2017 at 5:35 AM, Jason Orendorff 

> 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?
> 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.")
> -j
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