empty_child_inc/dec() use the ternary operator for conditional operations. The conditions involve the post/pre in/decrement operator and the operation is only performed when the condition is *not* true. This is hard to parse for humans, use a regular 'if' construct instead and perform the in/decrement separately.
This also fixes two warnings that are emitted about the value of the ternary expression being unused, when building the kernel with clang + "kbuild: Remove unnecessary -Wno-unused-value" (https://lore.kernel.org/patchwork/patch/1089869/): CC net/ipv4/fib_trie.o net/ipv4/fib_trie.c:351:2: error: expression result unused [-Werror,-Wunused-value] ++tn_info(n)->empty_children ? : ++tn_info(n)->full_children; Signed-off-by: Matthias Kaehlcke <m...@chromium.org> --- I have no good understanding of the fib_trie code, but the disentangled code looks wrong, and it should be equivalent to the cryptic version, unless I messed it up. In empty_child_inc() 'full_children' is only incremented when 'empty_children' is -1. I suspect a bug in the cryptic code, but am surprised why it hasn't blown up yet. Or is it intended behavior that is just super-counterintuitive? For now I'm leaving it at disentangling the cryptic expressions, if there is a bug we can discuss what action to take. --- net/ipv4/fib_trie.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 868c74771fa9..cf7788e336b7 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -338,12 +338,18 @@ static struct tnode *tnode_alloc(int bits) static inline void empty_child_inc(struct key_vector *n) { - ++tn_info(n)->empty_children ? : ++tn_info(n)->full_children; + tn_info(n)->empty_children++; + + if (!tn_info(n)->empty_children) + tn_info(n)->full_children++; } static inline void empty_child_dec(struct key_vector *n) { - tn_info(n)->empty_children-- ? : tn_info(n)->full_children--; + if (!tn_info(n)->empty_children) + tn_info(n)->full_children--; + + tn_info(n)->empty_children--; } static struct key_vector *leaf_new(t_key key, struct fib_alias *fa) -- 2.22.0.410.gd8fdbe21b5-goog
