How ild Works

On an initial link, ild saves information about:

• All of the object files looked at.

• The symbol table for the executable produced

• All symbolic references not resolved at compile time

Initial ild links take about as much time as an ld link.

On incremental links, ild:

• Determines which files have changed

• Relinks the modified object files

• Uses stored information to modify changed symbolic references in the rest of the program

Incremental ild links are much faster than ld links.

In general, you do one initial link and all subsequent links are incremental.

For example, ild saves a list of all places where symbol foo is referenced in your code. If you do an incremental link that changes the value of foo, ild must change the value of all references to foo.

ild spreads out the components of the program and each section of the executable has padding added to it. Padding makes the executable modules larger than when they were linked by ld. As object files increase in size during successive incremental links, the padding can become exhausted. If this occurs, ild displays a message and does a complete full relink of the executable.

For example, as shown in Figure B-1, each of the three columns shows the sequence of text and data in a linked executable program. The left column shows text and data in an executable linked by ld. The center column shows the addition of text and data padding in an executable linked by ild. Assume that a change is made to the source file for Text 1 that causes the Text section to grow without affecting the size of the other sections. The right column shows that the original location of Text 1 has been replaced by Text padding (Text 1 has been invalidated). Text 1 has been moved to occupy a portion of the Text padding space.

To produce a smaller nonincremental executable, run the compiler driver (for example, cc or CC) with the -xildoff option, and ld is invoked to produce a more compact executable.

The resulting executable from ild can be debugged by dbx because dbx/Debugger understands the padding that ild inserts between programs.

For any command-line option that ild does not understand, ild invokes ld. ild is compatible with ld (in /usr/ccs/bin/ld). See "Options", for details.

There are no special or extra files used by ild.