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Gunderson" , Athira Rajeev , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/5] perf disasm: Avoid undefined behavior in incrementing NULL In-Reply-To: <20250821163820.1132977-2-irogers@google.com> References: <20250821163820.1132977-1-irogers@google.com> <20250821163820.1132977-2-irogers@google.com> Date: Thu, 21 Aug 2025 15:39:18 -0700 Message-ID: <87h5y09u5l.fsf@gmail.com> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Ian Rogers writes: > Incrementing NULL is undefined behavior and triggers ubsan during the > perf annotate test. Split a compound statement over two lines to avoid > this. > > Fixes: 98f69a573c66 ("perf annotate: Split out util/disasm.c") > Signed-off-by: Ian Rogers > Acked-by: Namhyung Kim > --- > tools/perf/util/disasm.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c > index b1e4919d016f..e257bd918c89 100644 > --- a/tools/perf/util/disasm.c > +++ b/tools/perf/util/disasm.c > @@ -390,13 +390,16 @@ static int jump__parse(struct arch *arch, struct ins_operands *ops, struct map_s > * skip over possible up to 2 operands to get to address, e.g.: > * tbnz w0, #26, ffff0000083cd190 > */ > - if (c++ != NULL) { > + if (c != NULL) { > + c++; > ops->target.addr = strtoull(c, NULL, 16); > if (!ops->target.addr) { > c = strchr(c, ','); > c = validate_comma(c, ops); > - if (c++ != NULL) > + if (c != NULL) { > + c++; > ops->target.addr = strtoull(c, NULL, 16); > + } > } > } else { > ops->target.addr = strtoull(ops->raw, NULL, 16); It is undefined behavior, but works correctly with GCC and Clang. In Gnulib, we allow it and suggest using -fno-sanitize=pointer-overflow instead [1]. But I can understand that is not every projects preference. Therefore, this change looks good to me. Reviewed-by: Collin Funk Collin [1] https://www.gnu.org/software/gnulib/manual/html_node/Unsupported-Platforms.html