Make C file for create type - Mailing list pgsql-sql

Hallo,
I found a problem making new data type kata,expecially
when make the C file ,can anyone help me solve it. 

This error occur when I'm compiling the C file :
/usr/lib/gcc-lib/i586-suse-linux/3.3.1/../../../crt1.o(.text+0x18):
In function `_start':
../sysdeps/i386/elf/start.S:98: undefined reference to
`main'
collect2: ld returned 1 exit status

Here it's my code :
file3.c
-------
#include "postgres.h"

typedef struct kata
{ char kt[30];
} kata;

kata *input_kata(char *str);
char *output_kata(kata * kata);

kata *
input_kata(char *str)
{   char kt[30];   kata *result;
   if (sscanf(str, "( %s )", &kt) !=1)   {       printf ("error\n");return NULL;   }
   result = (kata *) malloc(sizeof(kata));   strcpy(result->kt,kt);   return result;
}

char *
output_kata(kata * kata)
{char kt[30];       char *result;
       strcpy(kt,kata->kt);
if (strcmp(kt,NULL))    return NULL;
result = (char *) malloc(60);sprintf(result, "(%s)", kata->kt);return result;
}

kata.sql
--------
CREATE FUNCTION input_kata(cstring)  RETURNS kata  AS '_OBJWD_/file3'  LANGUAGE C IMMUTABLE STRICT;

CREATE FUNCTION output_kata(kata)  RETURNS cstring  AS '_OBJWD_/file3'  LANGUAGE C IMMUTABLE STRICT;

CREATE TYPE kata (   INPUT = input_kata,   OUTPUT = output_kata
)



    
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