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I think you missed something in the parent comment. Bazel can skip compiling an output file if the hashes for its source code files + BUILD files have an artifa

• chriswarbo 8y ago
  > Bazel can skip compiling an output file if the hashes for its source code files + BUILD files have an artifact in the remote (or local) cache. This is what I mentioned in a sibling comment: we need some way to identify binaries that doesn't rely on their hash. Using the hash of their source code files and build instructions is one way to identify things (Nix also does this, as well as those of any dependencies (recursively)). A different approach is to assign each binary an arbitrary name and version, which is what Debian packages do; although this is less automatic and is more prone to conflicting IDs. > This requires reproducible builds or else you could introduce build errors when your build environment changes. No, this only requires that builds are robust. For example, scripting languages are pretty robust, since their "build" mostly just copies text files around, and they look up most dependencies at run time rather than linking them (or a hard-coded path) into a binary. Languages like C are more fragile, but projects like autotools have been attempting to make their builds robust across different environments for decades. In this sense, reproducibility is just another approach to robustness. Don't get me wrong, I'm a big fan of reproducibility; but caching build artefacts is somewhat tangential (although not completely orthogonal).