Multi-file Compilation
Before you set specific compiler options, you can decide whether you want to use multi-file compilation, which is an optimization technique.

Multi-file Compilation
Enables multi-file compilation from the group of project files that you have selected in the Workspace window.
You can use this option for the entire project or for individual groups of files. All C/C++ source files in such a group are compiled together using one invocation of the compiler.
This means that all files included in the selected group are compiled using the compiler options which have been set on the group or nearest higher enclosing node which has any options set. Any overriding compiler options on one or more files are ignored when building, because a group compilation must use exactly one set of options.
For information about how multi-file compilation is displayed in the Workspace window, see Workspace window.
Discard Unused Publics
Discards any unused public functions and variables from the compilation unit.
For more information about multi-file compilation and discarding unused public functions, see Multi-file compilation units.