Incremental link editing

As previously mentioned, the output of ld can be used as an input file to subsequent ld runs provided that the relocation information is retained in the initial run by using the -r option. With large applications, it may be desirable to partition the C programs into subsystems, link each subsystem independently, and then link edit the entire application.

The first two steps in the following example are described by giving an ld command line followed by the file of COFF ld directives that was used in that command. The third step is the final link edit.

   ld -r  -o outfile1  ifile1 infile1.o
   

           /* ifile1  */
           SECTIONS
           {
                   ss1:
                   {
                           f1.o
                           f2.o
   			...
                           fn.o
                   }
           }

   ld -r  -o outfile2  ifile2  infile2.o
   

           /* ifile2  */
           SECTIONS
           {
                   ss2:
                   {
                           g1.o
                           g2.o
   			...
                           gn.o
                   }
           }

   ld -o final.out outfile1 outfile2

There are two simple rules to follow when applying this technique to incrementally link COFF files:

• Intermediate link edits should have only SECTIONS declarations in the link edit command language file, and be concerned only with the formation of output sections from input files and input sections. No binding of output sections should be done in these runs.

• All allocation and memory directives, as well as any assignment statements, are included only in the final ld run.