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

["H.J. Lu" <hjl.tools@gmail.com>]

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.