This Linux kernel change "gcc-9: don’t warn about uninitialized btrfs extent_type variable" is included in the Linux 5.1 release. This change is authored by Linus Torvalds <torvalds [at] linux-foundation.org> on Wed May 1 12:19:20 2019 -0700. The commit for this change in Linux stable tree is 7e74e23 (patch).
gcc-9: don't warn about uninitialized btrfs extent_type variable The 'extent_type' variable does seem to be reliably initialized, but it's _very_ non-obvious, since there's a "goto next" case that jumps over the normal initialization. That will then always trigger the "start >= extent_end" test, which will end up never falling through to the use of that variable. But the code is certainly not obvious, and the compiler warning looks reasonable. Make 'extent_type' an int, and initialize it to an invalid negative value, which seems to be the common pattern in other places. Signed-off-by: Linus Torvalds <email@example.com>
There are 2 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.
fs/btrfs/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 82fdda8..2973608 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -6783,7 +6783,7 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode, u64 extent_start = 0; u64 extent_end = 0; u64 objectid = btrfs_ino(inode); - u8 extent_type; + int extent_type = -1; struct btrfs_path *path = NULL; struct btrfs_root *root = inode->root; struct btrfs_file_extent_item *item;