I mentioned above that a Fubsy build script can contain multiple phases, corresponding to the phases of Fubsy’s own execution. Those phases are:
- add command-line options and variables that the user can pass to fubsy (executes very early, so Fubsy can tell if the command line is valid without churning through lots of expensive dependency analysis)
- examine the build system to figure out which compilers, tools, libraries, etc. are present in order to influence later phases
- specifies the resources (files) involved in your build, constructing the graph of dependencies that will drive everything
- follow the graph of dependencies to rebuild out-of-date files (i.e. conditionally execute actions based on dependencies between related resources)
- remove some or all build products (typically used in a separate invocation of fubsy: running build and clean in the same invocation would be pointless)
All phases except main are optional; a build script with no main phase would have an empty dependency graph, so nothing to build.
Currently, Fubsy always runs the main phase to define the graph of dependencies, followed by the build phase to walk the graph and build stale or missing targets. When options is implemented, it will always run first, since main will depend on user-defined command-line options and variables.
The other phases depend on user actions. For example, the clean phase will run if and only if the user executes
The configure phase will run if the user executes
However, there will probably be circumstances under which Fubsy runs configure automatically, e.g. in a fresh working dir that has never been configured. This is all to be sorted out in the future.
So far, only main and build are implemented. The main phase must be explicitly provided in every build script, and the build phase is implicit. It’s unclear what it would mean if a build script provided an explicit build phase. It’s entirely possible that using the same mechanism to describe both explicitly coded phases like main and the implicit, behind-the-scenes build phase is a bad idea.