The invention provides a technique for generating minimal debugging type information in a distinguished compile unit while still supporting the debugging of classes for which the distinguished compile unit is not, in this module, being built or debugged, where the debugging information for the classes has been previously compiled into one or more object modules. On detecting a reference to a type in a program, the compiler inserts code into the module it is compiling to direct the linker where to locate the debugging information object module describing that type. Usually, the object module will be located in a separate link library, so the compiler directs the linker to add the debug library to the list of libraries from which it tries to resolve symbolic references, and to add a reference to an external linkage symbol defined in the object module describing the type. The linker will have to resolve this symbol by adding the debug library into the link.