fixed gh-140 in first approximation

src/box/tuple.cc

@@ -380,7 +380,10 @@ tuple_new(struct tuple_format *format, uint32_t field_count,
 {
 	size_t tuple_len = end - *data;
 
-	if (tuple_len != tuple_range_size(data, end, field_count))
+	uint32_t test_field_count = field_count;
+	if (tuple_len != tuple_range_size(data, end, &test_field_count))
+		tnt_raise(IllegalParams, "tuple_new(): incorrect tuple format");
+	if (test_field_count > 0)
 		tnt_raise(IllegalParams, "tuple_new(): incorrect tuple format");
 
 	struct tuple *new_tuple = tuple_alloc(format, tuple_len);

src/box/tuple.h

@@ -307,10 +307,10 @@ static inline size_t tuple_len(struct tuple *tuple)
 }
 
 static inline size_t
-tuple_range_size(const char **begin, const char *end, uint32_t count)
+tuple_range_size(const char **begin, const char *end, uint32_t *count)
 {
 	const char *start = *begin;
-	while (*begin < end && count-- > 0) {
+	while (*begin < end && (*count)-- > 0) {
 		size_t len = load_varint32(begin);
 		*begin += len;
 	}