securid5.c contains a case statement that sets rval for various SecurID 
conditions (ie: user entered a bad passcode, user is in new pin mode etc).  
This case statement never sets rval upon SUCCESS, which makes the function 
return an undeclared int rval every time the user enters a correct passcode.

After line 172 in securid5.c you should add:

        case ACM_OK:
                rval = ACM_OK;
                break;


There are also a number of things a user must know in order to get sudo 
compiled in a SecurID 5.* environment that are not in the documentation (they 
refer to outdated 4.* era .h and .a files).  Let me know if you want a 
description of that as well.