From: bugzilla@dpdk.org
To: dev@dpdk.org
Subject: [Bug 1289] rte_table: lookup functions have UB for ctz
Date: Fri, 15 Sep 2023 11:49:01 +0000 [thread overview]
Message-ID: <bug-1289-3@http.bugs.dpdk.org/> (raw)
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https://bugs.dpdk.org/show_bug.cgi?id=1289
Bug ID: 1289
Summary: rte_table: lookup functions have UB for ctz
Product: DPDK
Version: 23.11
Hardware: x86
OS: Linux
Status: UNCONFIRMED
Severity: normal
Priority: Normal
Component: other
Assignee: dev@dpdk.org
Reporter: qrealka@gmail.com
Target Milestone: ---
Macros 'lookup2_stage0_with_odd_support' can call rte_ctz with zero value
(pkt_mask), which is undefined behaviour based on the GCC manual:
https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html
Quote: "
Built-in Function: int __builtin_ctz (unsigned int x)
Returns the number of trailing 0-bits in x, starting at the least significant
bit position. If x is 0, the result is undefined.
"
It is confirmed by checking this code in GCC-13 with ASAN.
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