Starting with abuild version 1.0.3, it is possible to list
other build items in the build-also key of
any named build item's Abuild.conf file.
Starting with abuild version 1.1.4,
build-also keys can list entire trees and
also add options to include tree dependencies or other items at
or below the item's directory. When abuild adds any build item
to the build set, if that build item has a
build-also key, then any build items listed
there are also added to the build set. The operation of
expanding initial build set membership using the
build-also key is applied iteratively until
no more build items are added. The principal intended use of
this feature is to aid with setting up virtual
“top-level” build items. For example, if your system
consisted of multiple, independent subsystems and you wanted to
build all of them, you could create a build item that lists the
main items for each subsystem in a
build-also key.
Arguments to build-also may be as follows:
item:]item-name [-desc]
Add item-name to the build set.
The literal item: prefix may be omitted
for backward compatibility.
If the -desc option is given, all items at
or below the directory containing
item-name are also added to the
build set. This is equivalent to running abuild
--build=desc from
item-name's directory.
tree:tree-name
[-desc]
[-with-tree-deps]
If
tree:tree-name
is specified by itself, all items in the build tree named
tree-name are added to the build
set. This is equivalent to running abuild
--build=local somewhere in that tree.
If -desc appears as an option by itself, all
items at or below the directory containing the root of
tree-name are added to the build
set. This is equivalent to running abuild
--build=desc from the directory containing the root
of the tree.
If -with-tree-deps appears as an option by
itself, all items in all trees that
tree-name specifies as tree
dependencies are added to the build set in addition to all
items in tree-name itself. This
is equivalent to running abuild
--build=deptrees somewhere in that tree.
If -with-tree-deps and
-desc are both specified, the result is to
add the items that are in the
intersection of the two options
specified individually. In other words, all items that are
in any dependent tree and are at or
below the directory containing the root of the tree are added
to the build set. This is equivalent to running
abuild --build=descdeptrees at the root of
the build tree. Note that if you want the
union of -desc and
-with-tree-deps instead of the intersection,
you simply have to specify both
tree:tree-name
-desc and
tree:tree-name
-with-tree-deps in the
build-also key.
In older versions of abuild, the only way to force building of one build item to build another item was to declare dependencies or tree dependencies. This had several disadvantages, including the following:
Adding unnecessary dependencies puts needless constraints on build ordering and parallelism.
Using dependencies for this purpose is clumsy if there are multiple target types involved. It would require you to use a platform-specific dependency, which in turn could interfere with proper use of platform selectors.
Otherwise harmless interface variable name clashes or assignment issues could cause problems as a result of having two interfaces that were supposed to be independent being loaded together.
Whenever you want building of one build item to result in building of another build item and the first item doesn't need to use anything from the items it causes to be built, it is appropriate to use build-also instead of a dependency.