From: Segher Boessenkool <segher@kernel.crashing.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
npiggin@gmail.com, linux-mm@kvack.org, kaleshsingh@google.com,
joel@joelfernandes.org, akpm@linux-foundation.org,
linuxppc-dev@lists.ozlabs.org, Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH v5 5/9] powerpc/mm/book3s64: Update tlb flush routines to take a page walk cache flush argument
Date: Thu, 20 May 2021 07:17:10 -0500 [thread overview]
Message-ID: <20210520121710.GR10366@gate.crashing.org> (raw)
In-Reply-To: <87y2c9j1ov.fsf@mpe.ellerman.id.au>
Hi!
On Thu, May 20, 2021 at 05:37:20PM +1000, Michael Ellerman wrote:
> Segher Boessenkool <segher@kernel.crashing.org> writes:
> > On Tue, May 18, 2021 at 07:45:14PM -0500, Segher Boessenkool wrote:
> >> On Wed, May 19, 2021 at 10:26:22AM +1000, Michael Ellerman wrote:
> >> > Guenter Roeck <linux@roeck-us.net> writes:
> >> > > Ah, sorry. I wasn't aware that the following is valid C code
> >> > >
> >> > > void f1()
> >> > > {
> >> > > return f2();
> >> > > ^^^^^^
> >> > > }
> >> > >
> >> > > as long as f2() is void as well. Confusing, but we live and learn.
> >> >
> >> > It might be valid, but it's still bad IMHO.
> >> >
> >> > It's confusing to readers, and serves no useful purpose.
> >>
> >> And it actually explicitly is undefined behaviour in C90 already
> >> (3.6.6.4 in C90, 6.8.6.4 in C99 and later).
>
> We use gnu89, which presumably does not make it UB.
Indeed. That is kind of implied by the "as a GNU extension" below, but
some explicit statement would be better, yup.
> > ... but there is a GCC extension that allows this by default:
> > <https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wreturn-type>
> > For C only, warn about a 'return' statement with an expression in a
> > function whose return type is 'void', unless the expression type is
> > also 'void'. As a GNU extension, the latter case is accepted
> > without a warning unless '-Wpedantic' is used.
>
> There's no chance we'll ever enable -Wpedantic,
Good, because -pedantic adds a lot of much more annoying warnings as
well. I find this extension questionable (like Guenter says it is
confusing and has no purpose), so the only thing it is "good" for is it
causes long email threads ;-)
Other than those things it is harmless though.
> so I guess it's allowed
> for practical purposes. I guess clang must accept it too or we'd be
> seeing warnings from it.
Yup.
Segher
next prev parent reply other threads:[~2021-05-20 12:21 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 5:43 [PATCH v5 0/9] Speedup mremap on ppc64 Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 1/9] selftest/mremap_test: Update the test to handle pagesize other than 4K Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 2/9] selftest/mremap_test: Avoid crash with static build Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 3/9] mm/mremap: Use pmd/pud_poplulate to update page table entries Aneesh Kumar K.V
2021-05-18 20:04 ` Nathan Chancellor
2021-05-19 4:46 ` Aneesh Kumar K.V
2021-05-19 18:02 ` Nathan Chancellor
2021-05-20 2:18 ` Peter Xu
2021-05-20 8:26 ` Aneesh Kumar K.V
2021-05-20 12:46 ` Peter Xu
2021-05-20 13:23 ` Aneesh Kumar K.V
2021-05-20 13:37 ` Aneesh Kumar K.V
2021-05-20 14:57 ` Peter Xu
2021-05-20 19:06 ` Zi Yan
2021-05-20 20:01 ` Peter Xu
2021-05-20 20:25 ` Kalesh Singh
2021-04-22 5:43 ` [PATCH v5 4/9] powerpc/mm/book3s64: Fix possible build error Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 5/9] powerpc/mm/book3s64: Update tlb flush routines to take a page walk cache flush argument Aneesh Kumar K.V
2021-05-15 16:35 ` Guenter Roeck
2021-05-15 20:41 ` Andrew Morton
2021-05-15 23:05 ` Guenter Roeck
2021-05-17 8:40 ` Aneesh Kumar K.V
2021-05-17 13:38 ` Guenter Roeck
2021-05-17 13:55 ` Aneesh Kumar K.V
2021-05-17 14:18 ` Guenter Roeck
2021-05-19 0:26 ` Michael Ellerman
2021-05-19 0:45 ` Segher Boessenkool
2021-05-19 12:03 ` Segher Boessenkool
2021-05-19 13:37 ` Guenter Roeck
2021-05-19 14:20 ` Segher Boessenkool
2021-05-19 15:28 ` Guenter Roeck
2021-05-20 7:37 ` Michael Ellerman
2021-05-20 12:17 ` Segher Boessenkool [this message]
2021-05-19 1:08 ` Guenter Roeck
2021-05-20 11:38 ` Michael Ellerman
2021-05-20 11:56 ` Guenter Roeck
2021-04-22 5:43 ` [PATCH v5 6/9] mm/mremap: Use range flush that does TLB and page walk cache flush Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 7/9] mm/mremap: Move TLB flush outside page table lock Aneesh Kumar K.V
2021-05-20 15:26 ` Aneesh Kumar K.V
2021-05-20 16:57 ` Aneesh Kumar K.V
2021-05-21 2:40 ` Linus Torvalds
2021-05-21 3:03 ` Aneesh Kumar K.V
2021-05-21 3:28 ` Aneesh Kumar K.V
2021-05-21 6:13 ` Linus Torvalds
2021-05-21 12:50 ` Aneesh Kumar K.V
2021-05-21 13:03 ` Aneesh Kumar K.V
2021-05-21 16:03 ` Linus Torvalds
2021-05-21 16:29 ` Aneesh Kumar K.V
2021-05-24 14:24 ` Aneesh Kumar K.V
2021-05-21 15:24 ` Liam Howlett
2021-05-21 16:02 ` Aneesh Kumar K.V
2021-05-21 16:05 ` Linus Torvalds
2021-04-22 5:43 ` [PATCH v5 8/9] mm/mremap: Allow arch runtime override Aneesh Kumar K.V
2021-04-22 5:43 ` [PATCH v5 9/9] powerpc/mm: Enable move pmd/pud Aneesh Kumar K.V
2021-05-11 22:19 ` Andrew Morton
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