Re: [LTP] [PATCH v2 1/2] openat2: define _GNU_SOURCE and include <fcntl.h>

[Li Wang via ltp <ltp@lists.linux.it>]

On Wed, Feb 04, 2026 at 01:23:32PM +0100, Petr Vorel wrote:
> hi Li,
> 
> > On Fedora Rawhide (glibc 2.43+), libc exposes openat2() and struct open_how,
> > so our configure script defines HAVE_OPENAT2 and the fallback definition in
> > lapi/openat2.h gets skipped. But openat20*.c never included <fcntl.h> (and
> > lacked _GNU_SOURCE), so the libc-provided prototype and struct stayed hidden,
> > so compilation failed:
> 
> >   # uname -r
> >   6.18.0-65.fc44.x86_64
> 
> >   # rpm -qf /usr/include/fcntl.h
> >   glibc-devel-2.43-1.fc44.x86_64
> 
> >   # nm -D /usr/lib64/libc.so.6 | grep -w openat2
> >   00000000000eb890 W openat2@@GLIBC_2.43
> 
> >   # make -C testcase/kernel/syscalls/openat2
> >   openat201.c:27:62: error: invalid application of ‘sizeof’ to incomplete type ‘struct open_how’
> >     27 |         {&dir_fd, TEST_FILE, O_RDWR, S_IRWXU, 0, &how, sizeof(*how)},
> 
> > Define _GNU_SOURCE and include <fcntl.h> in openat2 tests to make the
> > prototype available and fix the build.
> 
> > Signed-off-by: Li Wang <liwang@redhat.com>
> > ---
> >  testcases/kernel/syscalls/openat2/openat201.c | 3 +++
> >  testcases/kernel/syscalls/openat2/openat202.c | 3 +++
> >  testcases/kernel/syscalls/openat2/openat203.c | 3 +++
> >  3 files changed, 9 insertions(+)
> 
> > diff --git a/testcases/kernel/syscalls/openat2/openat201.c b/testcases/kernel/syscalls/openat2/openat201.c
> > index ecd63b150..40ac2f6d9 100644
> > --- a/testcases/kernel/syscalls/openat2/openat201.c
> > +++ b/testcases/kernel/syscalls/openat2/openat201.c
> > @@ -4,6 +4,9 @@
> >   *
> >   * Basic openat2() test.
> >   */
> > +#define _GNU_SOURCE
> 
> Why _GNU_SOURCE? glibc test tst-openat2.c [1] which includes <fcntl.h>, uses
> struct open_how and test openat2() does not define it. Neither openat2() nor
> struct open_how are guarded by #ifdef __USE_GNU.
> 
> O_DIRECTORY is guarded by #ifdef __USE_XOPEN2K8 but this should be safe as we
> compile with -std=gnu99.
> 
> I mean it's not a big deal, but if it works without it please remove it.

From my test on Fedora-Rawhide, it doesn't work if not define it.
Let me double check. Maybe reply to you tomorrow.

> 
> [1] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/tst-openat2.c
> [2] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/bits/openat2.h
> 
> > +#include <fcntl.h>
> 
> Should not we use include lapi/fcntl.h?
> 
> > +
> >  #include "tst_test.h"
> >  #include "lapi/openat2.h"
> 
> lapi/openat2.h uses struct open_how directly, shouldn't be included lapi/fcntl.h
> there?

From my understand lapi/* are appendix for missing stuff in header file.

Test cases should only include standard header files, and lapi should
only be used in case of missing or conflicting header files.

-- 
Regards,
Li Wang


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