If you are passing an ABL character string to a shared library routine, you can pass it as a CHARACTER variable or expression. However, if you expect the shared library routine to modify the value, Progress Software Corporation recommends that you pass the ABL character string in a MEMPTR memory region as a null-terminated string. This is required if it is an OUTPUT parameter. Otherwise, the shared library routine might inappropriately modify ABL memory outside the bounds of the CHARACTER value with unpredictable results. Assuming ABL has allocated the memory for the string (using SET-SIZE), you then use the GET-STRING function to extract the CHARACTER value.

If the DLL allocates the memory as either a RETURN value or an OUTPUT parameter, you must use an OUTPUT MEMPTR. For a RETURN parameter, you can use GET-STRING (or another access function) directly on the MEMPTR on return. However, for an OUTPUT parameter, you must use the GET-POINTER-VALUE and SET-POINTER-VALUE functions to access the data on return. (For more information on the GET- and SET-POINTER-VALUE functions, see OpenEdge Development: ABL Reference.)