Re: Btrfs progs release 4.8 (32bit builds broken)

[Justin Maggard <jmaggard10@gmail.com>]

I saw a 32-bit build failure, but it looked like a legitimate bug,
unrelated to the compiler version.  Here's the trivial fix:

diff --git a/ioctl.h b/ioctl.h
index a7235c0..26a3a5a 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -606,7 +606,7 @@ struct btrfs_ioctl_send_args {
  * Size of structure depends on pointer width, was not caught.  Kernel handles
  * pointer width differences transparently
  */
-BUILD_ASSERT(sizeof(__u64 *) == 8
+BUILD_ASSERT(sizeof(__u64) == 8
             ? sizeof(struct btrfs_ioctl_send_args) == 72
             : (sizeof(void *) == 4
                ? sizeof(struct btrfs_ioctl_send_args) == 68

-Justin

On Wed, Oct 5, 2016 at 6:33 AM, David Sterba <dsterba@suse.cz> wrote:
> I got a report that the 32bit builds are broken. This seems to be caused
> by padding inserted (or not) into the structures and depends on a
> compiler version. The error messages may look cryptic, but if you see
> something like
>
> ioctl.h:570:1: note: in expansion of macro 'BUILD_ASSERT'
>  BUILD_ASSERT(sizeof(struct btrfs_ioctl_received_subvol_args) == 200);
>
> that means that the given structure has an unexpected size. Fixing that
> properly will probably lead to some tricks to force the exact size
> regardless of arch bits and compiler.
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