The xdconfig program generates two modules of code - a 'Config file' and a 'Code file'. The Config file defines the list of all widgets, and the enumerations and aliases which they use.
These are normally defined in terms of symbolic constants (eg XtRJustify), and the Config file must include the headers which #define these constants. If the Config file fails to compile because of an undefined symbol, add the header in which the symbol is defined to the Config headers list for the relevant family.
You can change the order of the headers using the arrow buttons.
See also: