8.9 Partial (Incremental) Linking

An output file that has been linked can be linked again with additional modules. This is known as partial linking or incremental linking. Partial linking allows you to partition large applications, link each part separately, and then link all the parts together to create the final executable program.

Follow these guidelines for producing a file that you will relink:

• The intermediate files produced by the linker must have relocation information. Use the --relocatable option when you link the file the first time. (See Section 8.4.3.2.)
• Intermediate files must have symbolic information. By default, the linker retains symbolic information in its output. Do not use the --no_sym_table option if you plan to relink a file, because --no_sym_table strips symbolic information from the output module. (See Section 8.4.22.)
• Intermediate link operations should be concerned only with the formation of output sections and not with allocation. All allocation, binding, and MEMORY directives should be performed in the final link.

Since the ELF object file format is used, input sections are not combined into output sections during a partial link unless a matching SECTIONS directive is specified in the link step command file.

• If the intermediate files have global symbols that have the same name as global symbols in other files and you want them to be treated as static (visible only within the intermediate file), you must link the files with the --make_static option (see Section 8.4.17.1).
• If you are linking C code, do not use --ram_model or --rom_model until the final linker. Every time you invoke the linker with the --ram_model or --rom_model option, the linker attempts to create an entry point. (See Section 8.4.25, Section 3.3.2.1, and Section 3.3.2.2.)

The following example shows how you can use partial linking: