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TMI: workcache progress
Sep. 3rd, 2013 06:06 pmI'm continuing to make progress on workcache/rustpkg integration. Today I realized that I'd been doing things a bit wrong, and that it would be important for rustpkg to declare all the inputs (for a particular package) before starting to do actual work (building).
Let me back up a bit, though. workcache is a library for tracking cached function results. A function, in this case, is the process of generating build artifacts (libraries and/or executables) from inputs (source files). workcache knows about declared inputs, discovered inputs, and discovered outputs. In the case of rustpkg:
The code I'd written so far was interleaving declaring inputs with doing actual work (building, which produces discovered output). That won't do, because when you look up a cached function result, you're looking it up by the name of the function paired with the list of declared inputs. If you don't know all the inputs yet, you won't get the right function result, and you also won't save it in a way that lets it be found later.
So, I fixed that, and am putting it all back together now. It's slow going since workcache is not entirely documented (although it has more documentation than some Rust libraries do!) and I've had to add functionality to it.
Let me back up a bit, though. workcache is a library for tracking cached function results. A function, in this case, is the process of generating build artifacts (libraries and/or executables) from inputs (source files). workcache knows about declared inputs, discovered inputs, and discovered outputs. In the case of rustpkg:
- A declared input is a source file that you know about when you start building. For example, if the user wanted to build package foo in someworkspace, and someworkspace/src/foo/lib.rs exists, then you know that someworkspace/src/foo/lib.rs is a declared input.
- A discovered input is a source file or binary file that you discover while searching for dependencies. In the previous example, if lib.rs contains extern mod bar, and rustpkg determines that bar lives in $HOME/.rust/lib/libbar-whatever-someversion.dylib, then $HOME/.rust/lib/libbar-whatever-someversion.dylib gets added as a discovered input.
- A discovered output is what you're trying to build when you build the package. So, in this example, someworkspace/lib/libfoo-whatever-someversion.dylib would be a discovered output.
The code I'd written so far was interleaving declaring inputs with doing actual work (building, which produces discovered output). That won't do, because when you look up a cached function result, you're looking it up by the name of the function paired with the list of declared inputs. If you don't know all the inputs yet, you won't get the right function result, and you also won't save it in a way that lets it be found later.
So, I fixed that, and am putting it all back together now. It's slow going since workcache is not entirely documented (although it has more documentation than some Rust libraries do!) and I've had to add functionality to it.