How to send a string to CVI .c and get string return through TestStand sequence?

Question

Hi, I am using TestStand 3.1 and I have the StringConverter.c with CVI 8.0 with the function:
char * string_concat_2 (char* str1,char* str2)
 char * str_ret;
 str_ret = calloc(200, sizeof(char*));
 str_ret = strcat (str_ret, str1);
 str_ret = strcat (str_ret, str2);
 return str_ret;
I would like to use it  through Teststand, so I add a sequence using 'StringValueTest'. I Spectify Module CVI &  link to StringConverter.c and type in Function Name: char * string_concat_2 (char* str1,char* str2)
1. How I define to send the string1 ("Hello") & string2 ("World") to the Module?
2. How I define to string return ("HelloWorld" from the Module?
Thanks

Answer 1

Hi plit string,
You will need to have a parameter passed by reference to return the
string.  To do this, use a "C String Buffer" instead of a "C String
(const)" parameter type.  There is documentation on this in TestStand
Help.  Here is a quote from there:
"When using string parameters, use the C String Buffer or Unicode
String Buffer type if you want the function to be able to change the contents of
the argument in TestStand. Use the C String or Unicode String type if the DLL
function does not modify the argument. You can pass a literal string, a
TestStand string property, or an expression that evaluates to a string as the
value of a string parameter."
Gavin Fox
Systems Software
National Instruments