ICS 121: Automated Builds

What is a build system?
- Automates the steps needed to transform source code into object code and other deliverables
- This is not simply a single step to do a compilation, it is many steps
- Executable code is not the only deliverable that needs to be built. Other deliverables include generated documentation, test reports, and packaged code.
Why use a build system?
- Manually running build steps is tedious, error prone, and hard to communicate
- Automated builds enable automation of larger processes, e.g., deployment or testing
- Older goal: Optimize compilation time
Build system history:
- Older build systems, like 'make', were usually run by the developer from the command-line. Makefiles were complex and error-prone.
- When IDEs became popular, they hid the build system by automatically generating the same complext makefiles and running them with one keystroke. That worked well, so long as everyone used the same IDE manually.
- Now, Ant uses a much simpler configuration file and works from the command-line (allowing automation) or from within several different IDEs.

Source files: source code in a programming language, or input files to other tools, e.g. code or doc generators
Object files: the output of compilers or other tools.
- The output of one tool could be the input of another, e.g., generated code
- Object files are called "Object" files because they are the "objective" or "goal" of the build process.
Dependency: a logical relationship between source and object files. When a source file changes, the dependant object files must be updated.
Build file: instructions to the build system
- Often called a 'makefile' by people who have used 'make' for years
- Like a small program in a langauge that is specialized for builds
- Target: Like a procedure/method, typically generates one object file, or a set of related object files
- Targets can depend on objects that are produced by other targets
- One target is the default target