Shake features a built in "lint" features to check the build system is well formed. To run use
build --lint. You are likely to catch more lint violations if you first
build clean. The lint features are listed in this document. There is a performance penalty for building with
--lint, but it is typically small.
--lint. Detects changing the current directory, typically with
setCurrentDirectory. You should never change the current directory within the build system as multiple rules running at the same time share the current directory. You can still run
cmd_ calls in different directories using the
--lint. Detects if any files have changed after Shake has built them. There are a couple of causes for seeing this error:
- If there is a rule producing
foo.o, but another rule also modifies
- If you are on a file system where files change modification time after a while. A standard example would be an NFS drive where the underlying network file system stores modification times to second-level resolution, but the in-memory cache keeps them precisely.
- If you modify the build sources while running a build.
A consequence of this lint triggering would be that a subsequent build would do additional work, as it spots modifications.
needed is normally equivalent to
need, but with
--lint it also changes that the file does not change as a result of
need - expressing that you have already used the contents of the file.
--lint. The tracking function
trackWrite can be called to declare reads/writes, and they can assert various invariants about what files can be written where. Examples include:
- You can only read a file that is either your dependency, or a transitive dependency.
- You can only write a file that you are declared to write, or that no one calls
Additionally, you can ignore certain missing rules with
--lint-ignore=PATTERN. In general all files passed to
trackWrite are expected to be relative to the current directory, so
--lint-ignore patterns should match those relative paths.
fsatrace you can augment command line programs (called with
command) to automatically track which files they read and write, which turn into
trackWrite calls. To enable this feature pass
--lint-fsatrace=DIR passing the directories you want to lint. Passing
--lint-fsatrace is equivalent to
--lint-fsatrace=. - namely only lint the current directory.