Linking C++ and ESQL/C (with dttofmtasc function) on UNIX

We've Problem with using datetime conversion functions like dttofmtasc under Reliant UNIX Version 5.43. Our Problem: Linking C++ Objects and ESQL/C Objects with C++ Version 3.1C we've got the linking error 'undefined symbol dttofmtasc'. In the linking commandline we have put in all libs, like ESQL does (esql -lib). With the dump utility we find out, that the function is already in the libs. Does anybody know which command avoid this problem. Under Win95 and ESQL/C and Borland C++ the same sourcecode works. Thanks Oliver