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

[Athira Rajeev]

> On 14 Oct 2024, at 10:56 PM, Namhyung Kim <namhyung at kernel.org> wrote:
> 
> Hello Athira,
> 
> On Sun, Oct 13, 2024 at 11:07:42PM +0530, Athira Rajeev wrote:
>> 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 <atrajeev at linux.vnet.ibm.com>
> 
> 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
>> ---
>> 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