perf machine: Use path__join() to compose a path instead of snprintf(dir, '/', filename)

From: Arnaldo Carvalho de Melo <[email protected]>

Its more intention revealing, and if we're interested in the odd cases where this may end up truncating we can do debug checks at one centralized place.

Motivation, of all the container builds, fedora rawhide started complaining of:

util/machine.c: In function ‘machine__create_modules’:
util/machine.c:1419:50: error: ‘%s’ directive output may be truncated writing up to 255 bytes into a region of size between 0 and 4095 [-Werror=format-truncation=]
1419 | snprintf(path, sizeof(path), "%s/%s", dir_name, dent->d_name);
| ^~
In file included from /usr/include/stdio.h:894,
from util/branch.h:9,
from util/callchain.h:8,
from util/machine.c:7:
In function ‘snprintf’,
inlined from ‘maps__set_modules_path_dir’ at util/machine.c:1419:3,
inlined from ‘machine__set_modules_path’ at util/machine.c:1473:9,
inlined from ‘machine__create_modules’ at util/machine.c:1519:7:
/usr/include/bits/stdio2.h:71:10: note: ‘__builtin___snprintf_chk’ output between 2 and 4352 bytes into a destination of size 4096

There are other places where we should use path__join(), but lets get rid of this one first.

---
 tools/perf/util/machine.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index 44e40bad0e33..55a041329990 100644
@@ -16,6 +16,7 @@
 #include "map_symbol.h"
 #include "branch.h"
 #include "mem-events.h"
+#include "path.h"
 #include "srcline.h"
 #include "symbol.h"
 #include "sort.h"

@@ -1407,7 +1408,7 @@ static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, i
 		struct stat st;
 
 		/*sshfs might return bad dent->d_type, so we have to stat*/
-		snprintf(path, sizeof(path), "%s/%s", dir_name, dent->d_name);
+		path__join(path, sizeof(path), dir_name, dent->d_name);
 		if (stat(path, &st))
 			continue;
 

2.34.1