Re: [PATCH v3 0/3]

From: Jeff King <peff@peff.net>
Date: Jun 30, 2021, 17:45 UTC
Message-ID: <YNytp0JAIaQih0Y4@coredump.intra.peff.net>
In-Reply-To: <YNyrDxUO1PlGJvCn@coredump.intra.peff.net>

On Wed, Jun 30, 2021 at 01:34:07PM -0400, Jeff King wrote:

Show 16 quoted lines

> As an aside, having to have a separate bundle_header_init() and
> BUNDLE_HEADER_INIT is annoying (because they both must be kept up to
> date with each other), but quite common in our code base. I wonder if
> writing:
> 
>   void bundle_header_init(struct bundle_header *header)
>   {
> 	struct bundle_header blank = BUNDLE_HEADER_INIT;
> 	memcpy(header, &blank, sizeof(*header));
>   }
> 
> would let a smart enough compiler just init "header" in place without
> the extra copy (the performance of a single bundle_header almost
> certainly doesn't matter, but it might for other types).
> 
> Just musing. ;)

For my own curiosity, the answer is yes: https://godbolt.org/z/s54dc6ss9

With "gcc -O2" the memcpy goes away and we init "header" directly.

If we want to start using this technique widely, I don't think it should be part of your series, though. This probably applies to quite a few data structures, so it would make more sense to have a series which converts several.

-Peff