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From: "H.J. Lu" <hjl.tools@gmail.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: libc-alpha@sourceware.org, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org
Subject: Re: [PATCH liburing] examples/ucontext-cp.c: cope with variable SIGSTKSZ
Date: Mon, 19 Apr 2021 11:38:07 -0700	[thread overview]
Message-ID: <CAMe9rOpK08CJ5TdQ1fZJ2sGUVjHqoTHS2kT8EzDEejuodu8Ksg@mail.gmail.com> (raw)
In-Reply-To: <YH2VE2RdcH0ISvxH@stefanha-x1.localdomain>

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.

-- 
H.J.

  reply	other threads:[~2021-04-19 18:38 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-13 15:03 [PATCH liburing] examples/ucontext-cp.c: cope with variable SIGSTKSZ Stefan Hajnoczi
2021-04-19 14:34 ` Stefan Hajnoczi
2021-04-19 18:38   ` H.J. Lu [this message]
2021-04-22  9:59     ` Stefan Hajnoczi
2021-04-22 14:22       ` Stefano Garzarella
2021-04-23 14:13         ` Pavel Begunkov
2021-04-20  0:05   ` Paul Eggert

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