[llvm-dev] [cfe-dev] Modernizing LLVM Coding Style Guide and enforcing Clang-tidy

Piotr Padlewski via llvm-dev llvm-dev at lists.llvm.org
Mon Jan 9 10:31:51 PST 2017

2017-01-09 19:25 GMT+01:00 Mehdi Amini <mehdi.amini at apple.com>:

> On Jan 9, 2017, at 10:20 AM, Reid Kleckner via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> On Mon, Jan 9, 2017 at 7:25 AM, Piotr Padlewski via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>> 2017-01-09 16:15 GMT+01:00 Renato Golin <renato.golin at linaro.org>:
>>> On 9 January 2017 at 14:17, Piotr Padlewski via cfe-dev
>>> <cfe-dev at lists.llvm.org> wrote:
>>> > - prefer "using' instead of "typedef"
>>> > - use default member initialization
>>> > - use default, override, delete
>>> > - skip "virtual" with override
>>> I thought we had all of those already...
>>> Nope, some people use it, but I still see a lot of new code with
>> typedefs.
>> I would like to have it written in style guide so it will be easier to
>> convince to change in review.
> The last two are enforced by compiler warnings now. The second is hard
> because of bitfields.
> I object to the first. If you need a new type name, use a typedef. It's
> time honored and everyone, including C programmers, will know what you're
> doing. I don't understand why people push the new thing just for the sake
> of new-ness.
> `using` handles strictly more cases than  `typedef`, in particular partial
> specialization of templates. So because we’ll end up with `using` anyway,
> uniformity can be valuable. So that could be a motivation: since `using` is
> needed anyway, might be better to just use it always (I’m not saying it is
> a “strong” motivation though, just some piece of rational).
> (I also find that typedef of function pointers in particular are terrible,
> and `using` is much better for these, but that can be a matter of taste).
>> Mehdi

+1 Exactly this.
I don't think C programmer will not understand using. The "=" makes it much
simpler to read, even if it is the first time you see it, which is not the
case of typedef.

typedef MyType::NestedType (*fptr)(const MyOhterType&);
using fptr = MyType::NestedType (*)(const MyOhterType&);

Typedefs with function pointers are used in couple of places in LLVM and I
find it terible to read.

So it is not about new-ness. Trust me, I would never use typedef if using
was first :)
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