Re: [PATCH] tools/perf/tests: Fix compilation error with strncpy in tests/tool_pmu

On 14 Oct 2024, at 10:56 PM, Namhyung Kim [off-list ref] wrote:

Hello Athira,

On Sun, Oct 13, 2024 at 11:07:42PM +0530, Athira Rajeev wrote:

quoted

perf fails to compile on systems with GCC version11
as below:

In file included from /usr/include/string.h:519,
                from /home/athir/perf-tools-next/tools/include/linux/bitmap.h:5,
                from /home/athir/perf-tools-next/tools/perf/util/pmu.h:5,
                from /home/athir/perf-tools-next/tools/perf/util/evsel.h:14,
                from /home/athir/perf-tools-next/tools/perf/util/evlist.h:14,
                from tests/tool_pmu.c:3:
In function ‘strncpy’,
   inlined from ‘do_test’ at tests/tool_pmu.c:25:3:
/usr/include/bits/string_fortified.h:95:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
  95 |   return __builtin___strncpy_chk (__dest, __src, __len,
     |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  96 |                                   __glibc_objsize (__dest));
     |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

The compile error is from strncpy refernce in do_test:
strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));

This behaviour is not observed with GCC version 8, but observed
with GCC version 11 . This is message from gcc for detecting
truncation while using strncpu. Use snprintf instead of strncpy
here to be safe.

Signed-off-by: Athira Rajeev <redacted>

I found this issue now and thanks for the quick fix.  I will push to
perf-tools-next soon.

Thanks,
Namhyung

Sure

Thanks Namhyung for pulling in the change

Athira

quoted

---
tools/perf/tests/tool_pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/tool_pmu.c b/tools/perf/tests/tool_pmu.c
index 94d0dd8fd3cb..297cc8c55579 100644
--- a/tools/perf/tests/tool_pmu.c
+++ b/tools/perf/tests/tool_pmu.c

@@ -22,7 +22,7 @@ static int do_test(enum tool_pmu_event ev, bool with_pmu)

if (with_pmu)
snprintf(str, sizeof(str), "tool/%s/", tool_pmu__event_to_str(ev));
else
- strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));
+ snprintf(str, sizeof(str), "%s", tool_pmu__event_to_str(ev));

parse_events_error__init(&err);
ret = parse_events(evlist, str, &err);
-- 
2.43.5