Re: [PATCH liburing] examples/ucontext-cp.c: cope with variable SIGSTKSZ

[Stefano Garzarella <sgarzare@redhat.com>]

+Cc: io-uring@vger.kernel.org
+Cc: Pavel Begunkov <asml.silence@gmail.com>

Original message: 
https://www.spinics.net/lists/linux-block/msg67077.html

On Thu, Apr 22, 2021 at 10:59:42AM +0100, Stefan Hajnoczi wrote:
>On Mon, Apr 19, 2021 at 11:38:07AM -0700, H.J. Lu wrote:
>> On Mon, Apr 19, 2021 at 7:35 AM Stefan Hajnoczi <stefanha@redhat.com> wrote:
>> >
>> > On Tue, Apr 13, 2021 at 04:03:19PM +0100, Stefan Hajnoczi wrote:
>> > > The size of C arrays at file scope must be constant. The following
>> > > compiler error occurs with recent upstream glibc (2.33.9000):
>> > >
>> > >   CC ucontext-cp
>> > >   ucontext-cp.c:31:23: error: variably modified ‘stack_buf’ at file scope
>> > >   31 |         unsigned char stack_buf[SIGSTKSZ];
>> > >      |                       ^~~~~~~~~
>> > >   make[1]: *** [Makefile:26: ucontext-cp] Error 1
>> > >
>> > > The following glibc commit changed SIGSTKSZ from a constant value to a
>> > > variable:
>> > >
>> > >   commit 6c57d320484988e87e446e2e60ce42816bf51d53
>> > >   Author: H.J. Lu <hjl.tools@gmail.com>
>> > >   Date:   Mon Feb 1 11:00:38 2021 -0800
>> > >
>> > >     sysconf: Add _SC_MINSIGSTKSZ/_SC_SIGSTKSZ [BZ #20305]
>> > >   ...
>> > >   +# define SIGSTKSZ sysconf (_SC_SIGSTKSZ)
>> > >
>> > > Allocate the stack buffer explicitly to avoid declaring an array at file
>> > > scope.
>> > >
>> > > Cc: H.J. Lu <hjl.tools@gmail.com>
>> > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>> > > ---
>> > > Perhaps the glibc change needs to be revised before releasing glibc 2.34
>> > > since it might break applications. That's up to the glibc folks. It
>> > > doesn't hurt for liburing to take a safer approach that copes with the
>> > > SIGSTKSZ change in any case.
>> >
>> > glibc folks, please take a look. The commit referenced above broke
>> > compilation of liburing's tests. It's possible that applications will
>> > hit similar issues. Can you check whether the SIGSTKSZ change needs to
>> > be reverted/fixed before releasing glibc 2.34?
>> >
>>
>> It won't be changed for glibc 2.34.
>
>Thanks for the response, H.J. and Paul.
>
>In that case liburing needs this patch.
>

I think so:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>