Re: [LTP] [PATCH] configure.ac: fix mount_attr detection

[Petr Vorel <pvorel@suse.cz>]

Hi all,

[ Cc Li - question from Cyril at the end ]

Fabrice, thanks for fixing this long standing issue.

> Hi!
> > Commit b857f8723f30a4b9554bf6b0ff8fa52fd07e8b60 tried to fix build with
> > latest glibc which provides mount_attr in sys/mount.h. Unfortunately,
> > the following build failure is still raised because sys/mount is now
> > unconditionally included in include/lapi/fsmount.h:

> > In file included from fsconfig01.c:9:
> > ../../../../include/lapi/fsmount.h:55:8: error: redefinition of 'struct mount_attr'
> >    55 | struct mount_attr {
> >       |        ^~~~~~~~~~
> > In file included from ../../../../include/lapi/fsmount.h:14:
> > /home/autobuild/autobuild/instance-4/output-1/host/armeb-buildroot-linux-gnueabi/sysroot/usr/include/sys/mount.h:210:8: note: originally defined here
> >   210 | struct mount_attr
> >       |        ^~~~~~~~~~

> > Fixes:
> >  - http://autobuild.buildroot.org/results/4dbb72e1bf081afd3cd944571b9beeefc7608865

> > Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> > ---
> >  configure.ac | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)

> > diff --git a/configure.ac b/configure.ac
> > index c2b0f48e7..a6d8ac826 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -225,10 +225,10 @@ AC_CHECK_TYPES([struct __kernel_old_timeval, struct __kernel_old_timespec, struc

> >  AC_CHECK_TYPES([struct futex_waitv],,,[#include <linux/futex.h>])
> >  AC_CHECK_TYPES([struct mount_attr],,,[
> > -#ifdef HAVE_LINUX_MOUNT_H
> > -# include <linux/mount.h>
> > -#else
> > +#ifdef HAVE_MOUNT_SETATTR
> >  # include <sys/mount.h>
> > +#elif HAVE_LINUX_MOUNT_H
> > +# include <linux/mount.h>
> >  #endif
> >  ])

> I wonder if we can get this whole mess of two different fallback headers
> simplified. Looking at the glibc implementation it seems to include
> "linux/mount.h" if it does exist. So most reasonable solution would do
> the same I guess which we did before the commit you reference.

> @Li Wang where does the the sys/mount.h and linux/mount.h conflict? As
> far as I can tell the UAPI linux/mount.h never defined any functions,
> just constants, which should be solvable without the complex ifdefs, we
> just need to check for existence of the types and define them only if
> missing.

Quoting [1]:

The newer Glibc already provided wrapper for the series pidfd syscall,
so let's include the header file conditionally.

  # rpm -q glibc-devel
  glibc-devel-2.35.9000-31.fc37.ppc64le

  # rpm -ql glibc-devel | grep pidfd
  /usr/include/sys/pidfd.h

To get rid of compiling error from fedora-rawhide:

  tst_safe_macros.c: In function ‘safe_pidfd_open’:
  tst_safe_macros.c:135:16: error: implicit declaration of function ‘pidfd_open’ [-Werror=implicit-function-declaration]
  135 |         rval = pidfd_open(pid, flags);
      |

=> Li, does the problem still persists? If yes, I'd be for merging this patch.
Could you also test it on newest glibc in Fedora?

Cyril, FYI musl never includes linux headers (Rich Felker has always been
against this practise).

Kind regards,
Petr

[1] https://lore.kernel.org/ltp/20220805063401.1647479-2-liwang@redhat.com/

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