We are getting fake gcc warning when we compile with gcc9 (9.1.1): CC jvmti/libjvmti.o In file included from /usr/include/string.h:494, from jvmti/libjvmti.c:5: In function ‘strncpy’, inlined from ‘copy_class_filename.constprop’ at jvmti/libjvmti.c:166:3: /usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound depends on the length of the source argument [-Werror=stringop-overflow=] 106 | return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest)); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ jvmti/libjvmti.c: In function ‘copy_class_filename.constprop’: jvmti/libjvmti.c:165:26: note: length computed here 165 | size_t file_name_len = strlen(file_name); | ^~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors
First I wanted to disable the check, but now I think the code could be more straight forward. There's no need to check the source size, strncpy will do that. We just need to make sure the string is correctly terminated. Cc: Ben Gainey <ben.gai...@arm.com> Cc: Stephane Eranian <eran...@google.com> Link: http://lkml.kernel.org/n/tip-sve3b63c550wr907e6ui6...@git.kernel.org Signed-off-by: Jiri Olsa <jo...@kernel.org> --- tools/perf/jvmti/libjvmti.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c index aea7b1fe85aa..00fa0b7f1ad9 100644 --- a/tools/perf/jvmti/libjvmti.c +++ b/tools/perf/jvmti/libjvmti.c @@ -162,8 +162,8 @@ copy_class_filename(const char * class_sign, const char * file_name, char * resu result[i] = '\0'; } else { /* fallback case */ - size_t file_name_len = strlen(file_name); - strncpy(result, file_name, file_name_len < max_length ? file_name_len : max_length); + strncpy(result, file_name, max_length - 1); + result[max_length - 1] = 0; } } -- 2.21.0