HP 3000 Manuals HP 3000 Manuals
Link Editor/XL by Cary Coutant and Brad Ahlf--Information Technology Group LINK EDITOR/XL HP has developed a new Link Editor for MPE XL to take advantage of the Precision Architecture. The Link Editor replaces the Segmenter for all native mode program development. In addition to providing support for the new architecture, the Link Editor also supports more programming language features, offers an improved user interface, and implements new features that allow users more program development flexibility than ever before. Although some commands and terms have changed, it is still possible for Segmenter users to become accustomed to the Link Editor quickly. For complete information about the Link Editor, consult the HP Link Editor/XL Reference Manual, (P/N 32650-90030). Link Editor/XL Features The MPE XL Link Editor is used for creating program files, relocatable libraries, and executable libraries. The Link Editor offers an interactive user interface, complete with help and redo functions. Programs are built using the Link Editor's LINK command, which combines relocatable object files and produces a program file. The MPE XL compilers translate each source file into a separate relocatable object file. The Link Editor can link any number of relocatable object files at one time; it can also search any number of relocatable libraries to find library routines that are needed by the program. Relocatable libraries contain libraries of common routines that can be copied into the program as needed when the program is linked. These libraries can be built with the BUILDRL command, and library routines can be added from relocatable object files with the ADDRL command. Library routines can also be purged, copied from one library to another, and extracted from a library into a stand-alone object file. Executable libraries are libraries of pre-linked program modules containing common routines that can be loaded with a program when it is executed. These routines can be shared by many programs and are not copied into the program files. Executable libraries can be built with the BUILDXL command, and modules can be added from relocatable object files or from relocatable libraries with the ADDXL command. Modules can also be purged and copied from one library to another. The Link Editor also offers commands to list the contents of relocatable object files, relocatable libraries, executable libraries, and program files. There is also a batch interface: any single Link Editor command can be invoked directly from the CI by passing the command in the INFO string. In addition, the LINK command can be executed directly from the CI. Link Editor/XL versus Segmenter The most noticeable difference between the MPE V Segmenter and the MPE XL Link Editor is that the Segmenter's PREPARE command produces a program file from a single User Subprogram Library (USL) file, the Link Editor's LINK command uses one or more relocatable object files. On MPE XL, there is no USL file or equivalent. Instead, the compilers create new object files for each source file compiled, and the Link Editor reads each object file independently. Aside from the lack of a USL file, the LINK command is very similar to the PREPARE command. Most of the options are very similar. Relocatable libraries are created and updated similarly with the Segmenter and the Link Editor. Unlike the Segmenter, however, the Link Editor can search many relocatable libraries during a link operation, rather than just one. Because MPE XL is not based on a segmented architecture, there is also no limit on the amount of code that can be included from relocatable libraries. One subtle, but important, difference is caused by the way that the compilers work. On MPE V, the compilers added one Relocatable Binary Module (RBM) to the USL for each procedure, function, or subprogram in the source file, and each of these RBMs could be individually purged, copied, or replaced. On MPE XL, the compilers produce one relocatable object file for each source file, and procedures, functions, and subprograms cannot be individually accessed unless there is only one per source file. Executable Libraries (XLs) on MPE XL are similar to Segmented Libraries. The only distinction is due to the architecture. The segmented architecture of MPE V imposed limits on segment sizes; MPE XL imposes no limits on the size of the modules in an XL.