Add test case to ARR30-C

Author: Nikita Kraiouchkine

c/cert/test/rules/ARR30-C/DoNotFormOutOfBoundsPointersOrArraySubscripts.expected

@@ -1,3 +1,5 @@
 | test.c:8:3:8:11 | ... + ... | Buffer accesses offset 404 which is greater than the fixed size 400 of the $@. | test.c:8:3:8:5 | arr | buffer |
 | test.c:16:3:16:13 | ... + ... | Buffer access may be to a negative index in the buffer. | test.c:16:3:16:5 | arr | buffer |
 | test.c:21:5:21:15 | ... + ... | Buffer access may be to a negative index in the buffer. | test.c:21:5:21:7 | arr | buffer |
+| test.c:41:17:41:30 | ... + ... | Buffer access may be to a negative index in the buffer. | test.c:41:17:41:22 | buffer | buffer |
+| test.c:45:17:45:30 | ... + ... | Buffer accesses may access up to offset 101*1 which is greater than the fixed size 100 of the $@. | test.c:45:17:45:22 | buffer | buffer |

c/cert/test/rules/ARR30-C/test.c

@@ -32,4 +32,20 @@ void test_valid_check_by_type(unsigned int index) {
   if (index < ARRAY_SIZE) {
     arr + index; // COMPLIANT - `index` cannot be be negative
   }
+}
+
+void test_local_buffer_invalid_check(int index) {
+  char buffer[ARRAY_SIZE];
+
+  if (index < ARRAY_SIZE) {
+    char *ptr = buffer + index; // NON_COMPLIANT - `index` could be negative
+  }
+
+  if (index >= 0 && index < ARRAY_SIZE + 2) {
+    char *ptr = buffer + index; // NON_COMPLIANT - `index` could be too large
+  }
+
+  if (index >= 0 && index < ARRAY_SIZE) {
+    char *ptr = buffer + index; // COMPLIANT
+  }
 }