some error about udf implement

[daikon12]

There is a error reported when I create a udf named belong.
ERROR 1105 (HY000): errCode = 2, detailMessage = VARCHAR size must be > 0: -1

The general create content ：
CREATE FUNCTION belong(VARCHAR,VARCHAR,VARCHAR,...) RETURNS BOOLEAN PROPERTIES (
"symbol" = "ZN9doris_udf6BelongEPNS_15FunctionContextERKNS_9StringValES4_iPS3",
"name" = "demo.belong",
"object_file" = "https:XXXXXXX"
);

The function definition in udf_belong.h ：
BooleanVal Belong(FunctionContext* ,const StringVal& str,const StringVal& sep,int num_in, const StringVal* in_strs);

Please tell me the reason for the error and the solution。

extremely grateful ！

[ChPi]

try belong(VARCHAR(256) instead of belong(VARCHAR

[daikon12]

thanks for the guide, it worked.