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From: Arvind Sankar <nivedita@alum.mit.edu>
To: Sedat Dilek <sedat.dilek@gmail.com>
Cc: "Fangrui Song" <maskray@google.com>,
	"Nick Desaulniers" <ndesaulniers@google.com>,
	"Joe Perches" <joe@perches.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Dávid Bolvanský" <david.bolvansky@gmail.com>,
	"Eli Friedman" <efriedma@quicinc.com>,
	"# 3.4.x" <stable@vger.kernel.org>,
	"Arvind Sankar" <nivedita@alum.mit.edu>,
	"Sami Tolvanen" <samitolvanen@google.com>,
	"Vishal Verma" <vishal.l.verma@intel.com>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Joel Fernandes (Google)" <joel@joelfernandes.org>,
	"Daniel Axtens" <dja@axtens.net>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Yury Norov" <yury.norov@gmail.com>,
	"Alexandru Ardelean" <alexandru.ardelean@analog.com>,
	LKML <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	"Rasmus Villemoes" <linux@rasmusvillemoes.dk>
Subject: Re: [PATCH v2] lib/string.c: implement stpcpy
Date: Sun, 16 Aug 2020 11:02:17 -0400	[thread overview]
Message-ID: <20200816150217.GA1306483@rani.riverdale.lan> (raw)
In-Reply-To: <CA+icZUW=rQ-e=mmYWsgVns8jDoQ=FJ7kdem1fWnW_i5jx-6JzQ@mail.gmail.com>

On Sun, Aug 16, 2020 at 07:22:35AM +0200, Sedat Dilek wrote:
> On Sun, Aug 16, 2020 at 2:19 AM 'Fangrui Song' via Clang Built Linux
> <clang-built-linux@googlegroups.com> wrote:
> >
> > Adding a definition without a declaration for stpcpy looks good.
> > Clang LTO will work.
> >
> > (If the kernel does not want to provide these routines,
> > is http://git.kernel.org/linus/6edfba1b33c701108717f4e036320fc39abe1912
> > probably wrong? (why remove -ffreestanding from the main Makefile) )
> >
> 
> We had some many issues in arch/x86 where *FLAGS were removed or used
> differently and had to re-add them :-(.
> 
> So if -ffreestanding is used in arch/x86 and was! used in top-level
> Makefile - it makes sense to re-add it back?
> ( I cannot speak for archs other than x86. )
> 
> - Sedat -

-ffreestanding disables _all_ builtins and libcall optimizations, which
is probably not desirable. If we added it back, we'd need to also go
back to #define various string functions to the __builtin versions.

Though I don't understand the original issue, with -ffreestanding,
sprintf shouldn't have been turned into strcpy in the first place.

32-bit still has -ffreestanding -- I wonder if that's actually necessary
any more?

Why does -fno-builtin-stpcpy not work with clang LTO? Isn't that a
compiler bug?

Thanks.

  reply	other threads:[~2020-08-16 15:03 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-15  0:24 [PATCH] lib/string.c: implement stpcpy Nick Desaulniers
2020-08-15  0:52 ` Joe Perches
2020-08-15  2:00   ` Nick Desaulniers
2020-08-15  0:53 ` Sami Tolvanen
2020-08-15  1:33 ` Arvind Sankar
2020-08-15  1:40   ` Arvind Sankar
2020-08-15  2:09     ` [PATCH v2] " Nick Desaulniers
2020-08-15  2:58       ` Arvind Sankar
2020-08-15  3:42       ` Joe Perches
2020-08-15 16:34       ` Kees Cook
2020-08-15 17:38         ` Dávid Bolvanský
2020-08-15 20:47         ` Nick Desaulniers
2020-08-15 21:23           ` Joe Perches
2020-08-15 21:27             ` Dávid Bolvanský
2020-08-15 21:28             ` Nick Desaulniers
2020-08-15 21:31               ` Joe Perches
2020-08-15 22:17                 ` Nick Desaulniers
2020-08-16  0:19                   ` Fangrui Song
2020-08-16  5:22                     ` Sedat Dilek
2020-08-16 15:02                       ` Arvind Sankar [this message]
2020-08-17 17:14                         ` Sami Tolvanen
2020-08-17 18:36                           ` Nick Desaulniers
2020-08-17 19:15                             ` Kees Cook
2020-08-17 20:13                             ` Arvind Sankar
2020-08-17 21:45                               ` Nick Desaulniers
     [not found]                             ` <77557c29286140dea726cc334b4f59fc@AcuMS.aculab.com>
2020-08-18  8:32                               ` Joe Perches
2020-08-17 19:16                           ` Kees Cook
2020-08-15  2:00   ` [PATCH] " Nick Desaulniers
2020-08-15 22:17 ` David Laight

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