add some test cases for empty check

diff --git a/test/test_utf8.c b/test/test_utf8.c
index 286158d053118df5e9c5377d3c72d301d9e7da9a..bd3ed1650f7ad0e63212f0be73ff1b4e621c1eb4 100644 (file)
--- a/test/test_utf8.c
+++ b/test/test_utf8.c
@@ -595,6 +595,10 @@ extern int main(int argc, char* argv[])
   x2("a\\Kb", "ab", 1, 2);
   x2("(a\\Kb|ac\\Kd)", "acd", 2, 3);
   x2("(a\\Kb|\\Kac\\K)*", "acababacab", 9, 10);
+  x2("(?:()|())*\\1", "abc", 0, 0);
+  x2("(?:()|())*\\2", "abc", 0, 0);
+  x2("(?:()|()|())*\\3\\1", "abc", 0, 0);
+  x2("(|(?:a(?:\\g'1')*))b|", "abc", 0, 2);
 
   x2("(?~)", "", 0, 0);
   x2("(?~)", "A", 0, 0);