[llvm-dev] Codifying our Brace rules-

Tue Jun 16 10:23:27 PDT 2020

I used to agree with the “always put braces unless it fits on a single line” camp, but it turns out that it’s really hard to break in a debugger on `statement;` if you write it `if (cond) statement;`

Personally, I’m in the “always put braces” camp. I think the many advantages to this approach have been stated by many people in this thread. The sole (that I’ve seen mentioned) disadvantage is “clutter”. However, I think in practice you learn to ignore the excess braces, especially since we write them like this:

```
if (foo) {
   bar;
} else if (baz) {
   quux;
}
```

That’s only one more line than:

```
if (foo)
   bar;
else if (baz)
   quux;
```

I had never mentioned anything because I have traumatic memories of endless arguments about coding style at previous orgs, but I would personally be strongly be in favor of the rule being “always put braces for the bodies of branches and loops”. Regardless, I think for the purposes of a body being “trivial”, comments on their own line, or statements broken across multiple lines should not be considered trivial:

```
if (foo)
   return nullptr; // this body is trivial

if (foo)
   // this body is no longer trivial
   return nullptr;

if (bar)
   GlobalState =
      doTheThing(this, body, is, no, longer, trivial);
```

Thanks,
   Christopher Tetreault

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Gabriel Hjort Åkerlund via llvm-dev
Sent: Tuesday, June 16, 2020 1:16 AM
To: jh7370.2008 at my.bristol.ac.uk; Matt Arsenault <arsenm2 at gmail.com>
Cc: llvm-dev at lists.llvm.org
Subject: [EXT] Re: [llvm-dev] Codifying our Brace rules-

I also prefer to always use braces even when not strictly necessary, for the same reasons as already mentioned. The only situation where I personally choose to remove the braces is when the statement fits on the same line as the condition, e.g.:

if (cond) statement;

In such cases, I find it clear that I need to add braces when expanding the statements.

But in case we want to be on the safe side I vote for always including braces, no matter what.

Gabriel

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces at lists.llvm.org>> On Behalf Of James Henderson via llvm-dev
Sent: den 16 juni 2020 10:02
To: Matt Arsenault <arsenm2 at gmail.com<mailto:arsenm2 at gmail.com>>
Cc: llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
Subject: Re: [llvm-dev] Codifying our Brace rules-

I'm with Matt on this one. I much prefer the approach of ALWAYS use braces for ifs and for loops, even if they're not needed, for basically the same reasons as he put. The number of times I've added a statement inside an if without braces and forget to add them is annoyingly high, especially as it's not always an obvious error upfront. Similarly, being involved in a downstream codebase with several private patches, having to sometimes add the braces makes merges all the harder and sometimes more dangerous.

I doubt we're going to get the policy changed from "don't include unnecessary braces for trivial statements" but if there's any style that adds them in more places, I'm up for that.

James

On Mon, 15 Jun 2020 at 20:56, Matt Arsenault via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:

On Jun 15, 2020, at 15:46, Keane, Erich via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:

Hi all-

A few weeks ago I noticed that our “omit braces with single line blocks” rule wasn’t written down!  Additionally, as a group on IRC and in review, noticed that the enforcement of this rule has been extremely inconsistent.  We made a first run at codifying our existing practice here: https://reviews.llvm.org/D80947<https://protect2.fireeye.com/v1/url?k=9efa459c-c04ad804-9efa0507-861fcb972bfc-42265df8dd683c0d&q=1&e=1cccb19d-3ee2-420f-b3a4-89ab398de655&u=https%3A%2F%2Freviews.llvm.org%2FD80947>, which was then committed after significant time on llvm-commits.

I would like to encourage the list via discussion and further reviews/commits to come to a consensus on what we actually MEAN by this rule.  For example, a recent comment points out that :

If (cond)
  Stmt;
else if (cond)
  Stmt;
else {
  Stmt;
  Stmt;
}

Should require braces on all of the conditions!  However, we are extraordinarily inconsistent here.  My wish is for us to become more consistent, so I would like us to use this thread to organize our collective thoughts on figuring out what the rule actually SHOULD be, and organizing a handful of commits to the coding standard to make sure it says what we mean.

Thanks,
Erich

I think braces should be added in all contexts, and the more contexts the better. It eliminates any inconsistency or attempt to contextually interpret rules. It also reduces merge conflicts, since something eventually something will probably be added inside any control flow statement. I’ve suffered through many painful merges trying to find where the braces went wrong, usually due to switch statements. The sometimes-braces-sometimes-not combined with the lack of indentation for switch cases leads to way more time figuring out braces than should be necessary.

-Matt
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