/sys$common/syshlp/helplib.hlb CC, Messages, LDCOMPLEXNYI  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        <Context> the type long double _Complex is not fully
                supported on this platform.  The type is only
                accepted when the compilation specifies the option to
                make the long double type 64-bits in size.

 Description    On some platforms Compaq C does not support the long
                double _Complex type where the real and imaginary
                component are 128-bits in size.  As Compaq C requires
                that each component of a long double _Complex be the
                same size as a long double, this compilation must
                specify the option to treat long double as 64-bits.

 User Action    Either specify the correct compiler option or use the
                double _Complex type instead of the long double
                _Complex type.