Re: [PATCH 1/2] selftests/memfd/memfd_test.c: fix implicit declaration

[Mike Kravetz <mike.kravetz@oracle.com>]

On 03/13/2018 04:42 AM, Anders Roxell wrote:
> gcc warns about implicit declaration.
> 
> gcc -D_FILE_OFFSET_BITS=64 -I../../../../include/uapi/
>     -I../../../../include/ -I../../../../usr/include/
>     memfd_test.c common.o  -o memfd_test
> memfd_test.c: In function ‘mfd_assert_get_seals’:
> memfd_test.c:74:6: warning: implicit declaration of function ‘fcntl’
>     [-Wimplicit-function-declaration]
>   r = fcntl(fd, F_GET_SEALS);
>       ^~~~~
> memfd_test.c: In function ‘mfd_assert_open’:
> memfd_test.c:197:6: warning: implicit declaration of function ‘open’
>     [-Wimplicit-function-declaration]
>   r = open(buf, flags, mode);
>       ^~~~
> memfd_test.c: In function ‘mfd_assert_write’:
> memfd_test.c:328:6: warning: implicit declaration of function ‘fallocate’
>     [-Wimplicit-function-declaration]
>   r = fallocate(fd,
>       ^~~~~~~~~
> 
> In the current code, we include the headers that the functions want
> according to the man pages, and we add some defines that will be used if
> they isn't found in glibc.  The defines was added into the kernel source
> in kernel >= 3.16 and glibc requires kernel header files >= 3.2.
> 
> Fixes: 4f5ce5e8d7e2 ("selftests: add memfd_create() + sealing tests")
> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
> ---
>  tools/testing/selftests/memfd/memfd_test.c | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
> index 10baa1652fc2..0dbeb29c094c 100644
> --- a/tools/testing/selftests/memfd/memfd_test.c
> +++ b/tools/testing/selftests/memfd/memfd_test.c
> @@ -6,7 +6,6 @@
>  #include <inttypes.h>
>  #include <limits.h>
>  #include <linux/falloc.h>
> -#include <linux/fcntl.h>
>  #include <linux/memfd.h>
>  #include <sched.h>
>  #include <stdio.h>
> @@ -14,13 +13,37 @@
>  #include <signal.h>
>  #include <string.h>
>  #include <sys/mman.h>
> +#include <sys/types.h>
>  #include <sys/stat.h>
>  #include <sys/syscall.h>
>  #include <sys/wait.h>
> +#include <fcntl.h>
>  #include <unistd.h>

I suspect there is some guiding philosophy for selftests that I am
unfamiliar with.  However, it seems that tests should use as much
of the header files in the current kernel source tree as possible.
This change removes the include of a header in the current source
tree <linux/fcntl.h>.  It replaces that with the header <fcntl.h>
from the host system (and some other changes).

To me, this seems like step in the wrong direction.  But, I could
be totally wrong and perhaps self tests should primarily target the
host system header files.
-- 
Mike Kravetz