perf srcline: Optimize comparision against SRCLINE_UNKNOWN

This is a string constant that gets returned and then strcmp() around,
we can instead just do a pointer comparision.

That requires a new global variable to comply with these warnings from
some versions of clang and gcc:

  41    68.95 fedora:rawhide                : FAIL clang version 16.0.4 (Fedora 16.0.4-1.fc39)
    result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare]
            if (start_line != SRCLINE_UNKNOWN &&
                           ^  ~~~~~~~~~~~~~~~  41

Ack comments:

Agreed, the strcmps make me nervous as they won't distinguish heap from
a global meaning we could end up with things like pointers to freed
memory. The comparison with the global is always going to be same imo.

Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ali Saidi <alisaidi@amazon.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Brian Robbins <brianrob@linux.microsoft.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: Fangrui Song <maskray@google.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ivan Babrou <ivan@cloudflare.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Steinar H. Gunderson <sesse@google.com>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Wenyu Liu <liuwenyu7@huawei.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Ye Xingchen <ye.xingchen@zte.com.cn>
Cc: Yuan Can <yuancan@huawei.com>
Link: https://lore.kernel.org/lkml/ZIcoJytUEz4UgQYR@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 0a10bcc6ec95..3dc8a4968beb 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -484,7 +484,7 @@ static int hist_entry__init(struct hist_entry *he,
 			goto err_infos;
 	}
 
-	if (he->srcline && strcmp(he->srcline, SRCLINE_UNKNOWN)) {
+	if (he->srcline && he->srcline != SRCLINE_UNKNOWN) {
 		he->srcline = strdup(he->srcline);
 		if (he->srcline == NULL)
 			goto err_rawdata;