[llvm-dev] Codifying our Brace rules-
Adrian McCarthy via llvm-dev
llvm-dev at lists.llvm.org
Fri Jun 26 09:30:51 PDT 2020
Thanks. Those latest tweaks about comment hoisting does clarify for me.
I'm not sure whether the code diffs are meant to promote one style above
the other. They are different styles that make different tradeoffs over
different features. Which one somebody prefers depends will depend on how
they value those features. It's nice to have some tangible examples to
compare though, so thanks for providing them.
On Thu, Jun 25, 2020 at 2:51 PM Mehdi AMINI <joker.eph at gmail.com> wrote:
>
> On Thu, Jun 25, 2020 at 2:14 PM Mehdi AMINI <joker.eph at gmail.com> wrote:
>
>>
>>
>> On Wed, Jun 24, 2020 at 5:35 PM Mehdi AMINI <joker.eph at gmail.com> wrote:
>>
>>>
>>>
>>> On Wed, Jun 24, 2020 at 11:51 AM Adrian McCarthy via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>>
>>>>
>>>> On Wed, Jun 24, 2020 at 2:37 AM Chris Lattner via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> On Jun 23, 2020, at 11:02 AM, Philip Reames <listmail at philipreames.com>
>>>>> wrote:
>>>>> > I'll note that reading along I haven't found any of the proposed
>>>>> changes particularly worthwhile. I'm also not strongly opposed to any of
>>>>> them - I just don't care - but I certainly haven't been convinced there's
>>>>> any clear benefit to be had by changing our current policy.
>>>>>
>>>>> I agree. The discussion is also hard to follow, because there are
>>>>> many different competing suggestions and opinions. There are a couple of
>>>>> people talking about clarifying the rules to be less prescriptive, which
>>>>> seem like it is worth discussing.
>>>>
>>>>
>>>> "Clarifying the rules to be less prescriptive" sounds
>>>> self-contradictory. Are you in favor of talking about clarifying the
>>>> existing guidelines or changing them to be less prescriptive? Or maybe you
>>>> want to change them a little so that they are easier to express clearly?
>>>>
>>>> There are already several well-defined de facto standard brace styles.
>>>> One way to make the guidelines clear (and concise) is simply to declare
>>>> LLVM uses $(FOO) Brace Style with a link to the Wikipedia description.
>>>> That suggests to me that it's not super feasible to divorce clarification
>>>> from style choice, at least, not without putting a bound on how clear we
>>>> can be.
>>>>
>>>>
>>>>> I think we should take the suggestion of “always require braces” off
>>>>> the table, because it doesn’t make sense given the impact to the code base.
>>>>>
>>>>
>>>> Given that the codebase is already riddled with inconsistencies (and
>>>> instances that I cannot determine the correctness against the current
>>>> guidelines), I don't understand why you think it doesn't make sense to
>>>> consider a simpler scheme. The current inconsistencies exist because the
>>>> rules are unclear and, because of the edge cases, hard to internalize. A
>>>> simpler rule (or set of rules) would presumably result in fewer
>>>> inconsistencies going forward, so the code would evolve toward a more
>>>> consistent state.
>>>>
>>>
>>> Can you clarify what is unclear with the current rule
>>> <https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements>
>>> ?
>>> The title of the section is "Don't Use Braces on Simple Single-Statement
>>> Bodies of if/else/loop Statements", which seems already fairly clear.
>>> It then also mentions exceptions to the rule: readability and
>>> maintainability ; and clarifies what is considered not readable and not
>>> maintainable. It even gives two examples.
>>>
>>> Maybe adding more examples there could help?
>>>
>>
>> Gave it a try here: https://reviews.llvm.org/D82594
>
> I'm fairly sure we can keep the spirit and write a clang-tidy rule that
> would cover most of the cases.
>
> I also ran an experiment adding all braces on one file:
> https://reviews.llvm.org/D82599
>
> And to be more representative, here is a visual diff (low quality for the
> mailing-list) of what it looks like in an editor for a single function
> (left is full braces, right is currently committed):
>
> [image: Screen Shot 2020-06-25 at 2.11.29 PM.jpg]
>
> Best,
>
> --
> Mehdi
>
>
> >
>>>>> > Philip
>>>>> >
>>>>> > On 6/22/20 1:44 PM, Chris Lattner via llvm-dev wrote:
>>>>> >> For those who don’t like it, is the currently documented policy
>>>>> broken enough to be important to changing?
>>>>> >>
>>>>> >> I assume you wouldn’t recommend a massive rewrite of the codebase,
>>>>> so we’re going to be with this for quite some time.
>>>>> >>
>>>>> >> -Chris
>>>>> >>
>>>>> >>> On Jun 22, 2020, at 1:36 PM, Steve Scalpone via llvm-dev <
>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>> >>>
>>>>> >>> Did this conversation reach a conclusion?
>>>>> >>>
>>>>> >>> My ad hoc tally says that a slight majority of the responders
>>>>> preferred to fully brace statements and no one wanted to totally eliminate
>>>>> braces.
>>>>> >>>
>>>>> >>> The technical arguments for fully braced statements were 1) it's
>>>>> considered a slightly safer coding style and 2) commit diffs with fully
>>>>> braced statements may be slightly more to the point.
>>>>> >>>
>>>>> >>> I didn't register any technical arguments for
>>>>> less-than-fully-braced statement -- the preference seemed to be aesthetic.
>>>>> I may have missed a technical argument.
>>>>> >>>
>>>>> >>> Certainly an "always use braces" rule would be simpler than what's
>>>>> documented now in the LLVM Coding Standards [1].
>>>>> >>>
>>>>> >>> Another option would be to make braces a developer's choice, and
>>>>> ask that those omitting braces please follow the rules documented in [1].
>>>>> >>>
>>>>> >>> [1]
>>>>> https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements
>>>>> >>>
>>>>> >>> On 6/18/20, 3:56 AM, "llvm-dev on behalf of Nicolai Hähnle via
>>>>> llvm-dev" <llvm-dev-bounces at lists.llvm.org on behalf of
>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>> >>>
>>>>> >>> External email: Use caution opening links or attachments
>>>>> >>>
>>>>> >>>
>>>>> >>> On Tue, Jun 16, 2020 at 10:35 AM Momchil Velikov via llvm-dev
>>>>> >>> <llvm-dev at lists.llvm.org> wrote:
>>>>> >>>> My 2 pennies is braces add unnecessary clutter and impair
>>>>> readability when
>>>>> >>>> used on a *single-line* statement. I count comments, that are on
>>>>> their
>>>>> >>>> own line as statement(s).
>>>>> >>> +1 for this. I think braces around single-line statements can be
>>>>> >>> allowed, but they really shouldn't be mandated, and that's been
>>>>> my
>>>>> >>> personal policy for reviews. In particular,
>>>>> >>>
>>>>> >>> if (!is_transform_applicable) {
>>>>> >>> return {};
>>>>> >>> }
>>>>> >>>
>>>>> >>> is very aggravating clutter.
>>>>> >>>
>>>>> >>> Braces should be required around multi-line statements. Note:
>>>>> >>>
>>>>> >>> BAD:
>>>>> >>> for (...)
>>>>> >>> for (...)
>>>>> >>> single_line_statement;
>>>>> >>>
>>>>> >>> GOOD:
>>>>> >>> for (...) {
>>>>> >>> for (...)
>>>>> >>> single_line_statement;
>>>>> >>> }
>>>>> >>>
>>>>> >>> Cheers,
>>>>> >>> Nicolai
>>>>> >>> --
>>>>> >>> Lerne, wie die Welt wirklich ist,
>>>>> >>> aber vergiss niemals, wie sie sein sollte.
>>>>> >>> _______________________________________________
>>>>> >>> LLVM Developers mailing list
>>>>> >>> llvm-dev at lists.llvm.org
>>>>> >>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>> >>>
>>>>> >>> _______________________________________________
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>>>>> >>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>> >> _______________________________________________
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>>>>>
>>>>> _______________________________________________
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>>>>>
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>>>
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