linux-kernel - Re: rfc: treewide scripted patch mechanism? (was: Re: [PATCH] Makefile: Convert -Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough for clang)QUILT

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Message-ID: <edd8efd53fadd07992f804cc595c6ae5fdb60e73.camel@perches.com>
Date:   Tue, 20 Aug 2019 17:20:43 -0700
From:   Joe Perches <joe@...ches.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Julia Lawall <julia.lawall@...6.fr>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux@...glegroups.com,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: rfc: treewide scripted patch mechanism? (was: Re: [PATCH]
 Makefile: Convert -Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough
 for clang)QUILT

On Tue, 2019-08-20 at 16:28 -0700, Linus Torvalds wrote:
> On Mon, Aug 19, 2019 at 5:08 PM Joe Perches <joe@...ches.com> wrote:
> > 2: would be Julia Lawall's stracpy change done
> > with coccinelle: (attached)
> 
> I'm not actually convinced about stracpy() and friends.
> 
> It seems to be yet another badly thought out string interface, and
> there are now so many of them that no human being can keep track of
> them.
> 
> The "badly thought out" part is that it (like the original strlcpy
> garbage from BSD) thinks that there is only one size that matters -
> the destination.
> 
> Yes, we fixed part of the "source is also limited" with strscpy(). It
> didn't fix the problem with different size limits, but at least it
> fixed the fundamentally broken assumption that the source has no size
> limit at all.

Umm, btw: have you actually looked at stracpy?

It's just a convenience wrapper around strscpy
and dest must be a char array and its size
does not need to be specified as a somewhat
useless argument otherwise prone to misuse.

#define stracpy(dest, src)						\
({									\
	size_t count = ARRAY_SIZE(dest);				\
	BUILD_BUG_ON(!(__same_type(dest, char[]) ||			\
		       __same_type(dest, unsigned char[]) ||		\
		       __same_type(dest, signed char[])));		\
									\
	strscpy(dest, src, count);					\
})

I sent several patches for those misuses.