From: Stefan Hajnoczi via Libc-alpha <libc-alpha@sourceware.org>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, libc-alpha@sourceware.org
Subject: Re: [PATCH liburing] examples/ucontext-cp.c: cope with variable SIGSTKSZ
Date: Thu, 22 Apr 2021 10:59:42 +0100 [thread overview]
Message-ID: <YIFJDgno7deI5syK@stefanha-x1.localdomain> (raw)
In-Reply-To: <CAMe9rOpK08CJ5TdQ1fZJ2sGUVjHqoTHS2kT8EzDEejuodu8Ksg@mail.gmail.com>
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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.
Stefan
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next prev parent reply other threads:[~2021-04-22 9:59 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 via Libc-alpha
2021-04-19 14:34 ` Stefan Hajnoczi via Libc-alpha
2021-04-19 18:38 ` H.J. Lu via Libc-alpha
2021-04-22 9:59 ` Stefan Hajnoczi via Libc-alpha [this message]
2021-04-22 14:22 ` Stefano Garzarella via Libc-alpha
2021-04-23 14:13 ` Pavel Begunkov via Libc-alpha
2021-04-20 0:05 ` Paul Eggert
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