Re: [PATCH] lib/string.c: implement stpcpy

Nick Desaulniers
2020-08-15T22:01:28Z

On Fri, Aug 14, 2020 at 5:52 PM Joe Perches <joe@perches.com> wrote:
>
> On Fri, 2020-08-14 at 17:24 -0700, Nick Desaulniers wrote:
> > LLVM implemented a recent "libcall optimization" that lowers calls to
> > `sprintf(dest, "%s", str)` where the return value is used to
> > `stpcpy(dest, str) - dest`. This generally avoids the machinery involved
> > in parsing format strings.
> []
> > diff --git a/include/linux/string.h b/include/linux/string.h
> []
> > @@ -31,6 +31,9 @@ size_t strlcpy(char *, const char *, size_t);
> > #ifndef __HAVE_ARCH_STRSCPY
> > ssize_t strscpy(char *, const char *, size_t);
> > #endif
> > +#ifndef __HAVE_ARCH_STPCPY
> > +extern char *stpcpy(char *__restrict, const char *__restrict__);
>
> Why use two different forms for __restrict and __restrict__?
> Any real reason to use __restrict__ at all?

Bah, sorry, I recently enabled some setting in my ~/.vimrc to help me
find my cursor better:
" highlight cursor
set cursorline
set cursorcolumn

Turns out this makes it pretty difficult to see underscores, or the
lack thereof. Will fix up.

>
> It's used nowhere else in the kernel.
>
> $ git grep -w -P '__restrict_{0,2}'
> scripts/genksyms/keywords.c: // According to rth, c99 defines "_Bool", __restrict", __restrict__", "restrict". KAO
> scripts/genksyms/keywords.c: { "__restrict__", RESTRICT_KEYW },
>
>

--
Thanks,
~Nick Desaulniers