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IMPORT: ebtree: Fix UB from clz(0)

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From 'man gcc': passing 0 as the argument to "__builtin_ctz" or
"__builtin_clz" invokes undefined behavior. This triggers UBsan
in HAProxy.

[wt: tested in treebench and verified not to cause any performance
 regression with opstime-u32 nor stress-u32]
Signed-off-by: Willy Tarreau <w@1wt.eu>
This is ebtree commit 8c29daf9fa6e34de8c7684bb7713e93dcfe09029.
Signed-off-by: Willy Tarreau <w@1wt.eu>
This is ebtree commit cf3b93736cb550038325e1d99861358d65f70e9a.
This commit is contained in:
Ben Kallus 2025-09-13 14:00:03 +02:00 committed by Willy Tarreau
parent 52c6dd773d
commit ddbff4e235
1 changed files with 8 additions and 6 deletions
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14
include/import/eb32tree.h
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@ -309,9 +309,6 @@ __eb32_insert(struct eb_root *root, struct eb32_node *new) {
* would sit on different branches).
*/
// note that if EB_NODE_BITS > 1, we should check that it's still >= 0
new->node.bit = flsnz(new->key ^ old->key) - EB_NODE_BITS;
if (new->key == old->key) {
new->node.bit = -1; /* mark as new dup tree, just in case */
@ -330,6 +327,10 @@ __eb32_insert(struct eb_root *root, struct eb32_node *new) {
}
/* otherwise fall through */
}
else {
/* note that if EB_NODE_BITS > 1, we should check that it's still >= 0 */
new->node.bit = flsnz(new->key ^ old->key) - EB_NODE_BITS;
}
if (new->key >= old->key) {
new->node.branches.b[EB_LEFT] = troot;
@ -446,9 +447,6 @@ __eb32i_insert(struct eb_root *root, struct eb32_node *new) {
* would sit on different branches).
*/
// note that if EB_NODE_BITS > 1, we should check that it's still >= 0
new->node.bit = flsnz(new->key ^ old->key) - EB_NODE_BITS;
if (new->key == old->key) {
new->node.bit = -1; /* mark as new dup tree, just in case */
@ -467,6 +465,10 @@ __eb32i_insert(struct eb_root *root, struct eb32_node *new) {
}
/* otherwise fall through */
}
else {
/* note that if EB_NODE_BITS > 1, we should check that it's still >= 0 */
new->node.bit = flsnz(new->key ^ old->key) - EB_NODE_BITS;
}
if ((s32)new->key >= (s32)old->key) {
new->node.branches.b[EB_LEFT] = troot;