Re: [PATCH] xfstests: replace custom __u64 definition with uint64_t

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Dec 21, 2023 at 11:42:31AM +0530, Disha Goel wrote:
> In some distributions, __u64 is already defined in system header files,
> causing compilation errors when building xfstest.
> 
> 	# make
> 	    [CC]    ext4_resize
> 	ext4_resize.c:17:28: error: conflicting types for '__u64'
> 	 typedef unsigned long long __u64;
> 	                            ^~~~~
> 	In file included from /usr/include/asm/types.h:26:0,
> 	                 from /usr/include/linux/types.h:5,
> 	                 from /usr/include/linux/mount.h:4,
> 	                 from /usr/include/sys/mount.h:32,
> 	                 from ext4_resize.c:15:
> 	/usr/include/asm-generic/int-l64.h:30:23: note: previous declaration of '__u64' was here
> 	 typedef unsigned long __u64;
>                        ^~~~~
> 
> To address this issue, replace the custom definition of __u64 with the
> standard uint64_t type from <stdint.h>. uint64_t is part of the C99
> standard, offering a standardised approach for representing unsigned
> 64-bit integers. This modification enhances code consistency and
> ensures compatibility with standard types.

...but isn't consistent with the definition in the kernel uapi headers.
ioctls explicitly use __u64, not uint64_t, and there are a few arches
(apparently) where __u64 ends up an unsigned long long but uint64_t ends
up an unsigned long, and the reverse.

> Tested on various distributions on Power architecture, by successfully
> compiling xfstest. Additionally, verified the compatibility by running
> ext4/033 and ext4/056 tests, both of which use ext4_resize and
> observed successful test execution.
> 
>         # make
>             [CC]    detached_mounts_propagation
>             [CC]    ext4_resize
>             [CC]    t_readdir_3
> 
> Signed-off-by: Disha Goel <disgoel@linux.ibm.com>
> ---
>  src/ext4_resize.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/src/ext4_resize.c b/src/ext4_resize.c
> index 78b66432..6e60ee5b 100644
> --- a/src/ext4_resize.c
> +++ b/src/ext4_resize.c
> @@ -14,10 +14,8 @@
>  #include <sys/ioctl.h>
>  #include <sys/mount.h>

Why not #include <linux/ext4.h>, which gets you both the __u64 typedef
and EXT4_IOC_RESIZE_FS?

--D

>  
> -typedef unsigned long long __u64;
> -
>  #ifndef EXT4_IOC_RESIZE_FS
> -#define EXT4_IOC_RESIZE_FS		_IOW('f', 16, __u64)
> +#define EXT4_IOC_RESIZE_FS		_IOW('f', 16, uint64_t)
>  #endif
>  
>  #define pr_error(fmt, ...) do { \
> @@ -31,7 +29,7 @@ static void usage(void)
>  
>  int main(int argc, char **argv)
>  {
> -	__u64	new_size;
> +	uint64_t	new_size;
>  	int	error, fd;
>  	char	*mnt_dir = NULL, *tmp = NULL;
>  
> -- 
> 2.39.1
> 
>