Improve ABI backward & forward compatibillity

 - Padd the compressor config union
    - 128 bytes aught to be enough for everyone, i.e. future compressors.
    - Insist that the padding space is initialized to 0. If a field gets
      added to an existing compressor, it can test for 0 as a sentinel
      value.
 - Add a size field to the hook structure, aka "the Microsoft way".
    - The explanation is in the comment.
    - Don't make the Microsoft mistake of checking for >=, insist on *exact*
      size match. Future users will need a fallback if their hooks are
      rejected. But at least they will be rejected instead of silently not
      being used.
 - Add an unsupported flag check to the dir tree reader.
 - Add a basic abi unit test that, for now, checks the size of the compressor
   config struct fields.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/sqfs/read_tree.c b/lib/sqfs/read_tree.c
index 46c7ec0..3a43769 100644
--- a/lib/sqfs/read_tree.c
+++ b/lib/sqfs/read_tree.c
@@ -199,6 +199,9 @@ int sqfs_dir_reader_get_full_hierarchy(sqfs_dir_reader_t *rd,
 	const char *ptr;
 	int ret;
 
+	if (flags & ~SQFS_TREE_ALL_FLAGS)
+		return SQFS_ERROR_UNSUPPORTED;
+
 	ret = sqfs_dir_reader_get_root_inode(rd, &inode);
 	if (ret)
 		return ret;