The Abuild.mk file is read by GNU Make and is a GNU Make fragment. It therefore has GNU Make syntax. The Abuild.mk file is intended to contain only variable settings. It contains no make rules or include directives. Abuild automatically includes your Abuild.mk file at the appropriate time and in the appropriate context.

The most important line in Abuild.mk is the setting of the RULES variable. Its purpose is to tell abuild which rule set should be used to generate targets from sources. Most of the remaining variables that are set are dependent upon which rules are being used. It is always possible to use abuild's help system to get detailed rule-specific help about what variables you are expected to define in your Abuild.mk for a specific set of rules. Run abuild --help help for additional information. Abuild provides some built-in rules. Additional rules may provided my plugins or items that you depend on. You can always run abuild --help rules list to get a list of rules that are available to your build item.

In rare instances, it may be necessary to create local rules for a specific build item. Examples may include one-off, special-purpose code generators that are specific to a particular build item. To use local rules, place a list of files that contain definitions of your rules in the LOCAL_RULES variable. Files listed there are resolved relative to the Abuild.mk. They may contain any valid GNU Make code. If you have written the same local rule in more than one or two places, you are probably doing something wrong and should be using build-item-specific rules (Chapter 22, Build Item Rules and Automatically Generated Code ) or plugins (Chapter 29, Enhancing Abuild with Plugins) instead.

Please note that local rules are run from the context of the output directory—you must keep this in mind when using relative paths from your local rules. The make variable SRCDIR is always set to a relative path to the directory that contains the Abuild.mk file. Also, local rules should avoid creating files outside of the output directory since these files will not be removed by the clean target.