shared: suppress -Wstringop-truncation warning in nm_strndup_a()

The compiler is too smart for nm_strndup_a(). The code is correct,
suppress "-Wstringop-truncation" warning.

2 files changed, 61 insertions, 1 deletions

diff --git a/shared/nm-utils/nm-shared-utils.h b/shared/nm-utils/nm-shared-utils.h
index 8106371d0a..93868726e8 100644
--- a/shared/nm-utils/nm-shared-utils.h
+++ b/shared/nm-utils/nm-shared-utils.h
@@ -255,10 +255,12 @@ nm_memdup (gconstpointer data, gsize size)
 static inline char *
 _nm_strndup_a_step (char *s, const char *str, gsize len)
 {
+	NM_PRAGMA_WARNING_DISABLE ("-Wstringop-truncation");
 	if (len > 0)
 		strncpy (s, str, len);
 	s[len] = '\0';
 	return s;
+	NM_PRAGMA_WARNING_REENABLE;
 }
 
 /* Similar to g_strndup(), however, if the string (including the terminating
@@ -269,7 +271,12 @@ _nm_strndup_a_step (char *s, const char *str, gsize len)
  *
  * In case malloc() is necessary, @out_str_free will be set (this string
  * must be freed afterwards). It is permissible to pass %NULL as @out_str_free,
- * if you ensure that len < alloca_maxlen. */
+ * if you ensure that len < alloca_maxlen.
+ *
+ * Note that just like g_strndup(), this always returns a buffer with @len + 1
+ * bytes, even if strlen(@str) is shorter than that (NUL terminated early). We fill
+ * the buffer with strncpy(), which means, that @str is copied up to the first
+ * NUL character and then filled with NUL characters. */
 #define nm_strndup_a(alloca_maxlen, str, len, out_str_free) \
 	({ \
 		const gsize _alloca_maxlen = (alloca_maxlen); \
diff --git a/shared/nm-utils/tests/test-shared-general.c b/shared/nm-utils/tests/test-shared-general.c
index d7df46dc52..7d22e56d99 100644
--- a/shared/nm-utils/tests/test-shared-general.c
+++ b/shared/nm-utils/tests/test-shared-general.c
@@ -152,6 +152,58 @@ test_nm_strdup_int (void)
 
 /*****************************************************************************/
 
+static void
+test_nm_strndup_a (void)
+{
+	int run;
+
+	for (run = 0; run < 20; run++) {
+		gs_free char *input = NULL;
+		char ch;
+		gsize i, l;
+
+		input = g_strnfill (nmtst_get_rand_int () % 20, 'x');
+
+		for (i = 0; input[i]; i++) {
+			while ((ch = ((char) nmtst_get_rand_int ())) == '\0') {
+				/* repeat. */
+			}
+			input[i] = ch;
+		}
+
+		{
+			gs_free char *dup_free = NULL;
+			const char *dup;
+
+			l = strlen (input) + 1;
+			dup = nm_strndup_a (10, input, l - 1, &dup_free);
+			g_assert_cmpstr (dup, ==, input);
+			if (strlen (dup) < 10)
+				g_assert (!dup_free);
+			else
+				g_assert (dup == dup_free);
+		}
+
+		{
+			gs_free char *dup_free = NULL;
+			const char *dup;
+
+			l = nmtst_get_rand_int () % 23;
+			dup = nm_strndup_a (10, input, l, &dup_free);
+			g_assert (strncmp (dup, input, l) == 0);
+			g_assert (strlen (dup) <= l);
+			if (l < 10)
+				g_assert (!dup_free);
+			else
+				g_assert (dup == dup_free);
+			if (strlen (input) < l)
+				g_assert (nm_utils_memeqzero (&dup[strlen (input)], l - strlen (input)));
+		}
+	}
+}
+
+/*****************************************************************************/
+
 NMTST_DEFINE ();
 
 int main (int argc, char **argv)
@@ -162,6 +214,7 @@ int main (int argc, char **argv)
 	g_test_add_func ("/general/test_nmhash", test_nmhash);
 	g_test_add_func ("/general/test_nm_make_strv", test_make_strv);
 	g_test_add_func ("/general/test_nm_strdup_int", test_nm_strdup_int);
+	g_test_add_func ("/general/test_nm_strndup_a", test_nm_strndup_a);
 
 	return g_test_run ();
 }