> All APIs are slightly unstable in some sense (even adding fields can be a breaking change)
Of course adding fields is a breaking change. It has never ceased to astonish me how little most programmers understand compatibility, I remember wrestling with libpng getting them to understand that e.g. no, "tidying up" the order of fields in a public structure you've published isn't safe back in the 1990s before they came to god and actually provided sane APIs which hide internal data structures.
Now, it's true that Hyrum's Law means any detectable change, even if it was never documented, will break somebody if there are enough people depending on your system. That's a big deal if you're the Linux kernel, or the HTTP/1.1 protocol, as it means even trivial "this can't break anything" fixes may break stuff. For example, as I understand it Google once broke search in Asia by changing an internal constant so that a hashmap would re-allocate (thus invalidating pointers to items in the map) slightly earlier. C++ code relying on pointers to just magically stay valid across inserts was completely wrong before they broke it, but anybody staring at a 500 page on google.com doesn't care why it broke they just want it fixed.
Most of us needn't much worry about Hyrum's law. That would be, as an old boss repeatedly told us, "A good problem to have" because it means you're having enormous impact.
Of course adding fields is a breaking change. It has never ceased to astonish me how little most programmers understand compatibility, I remember wrestling with libpng getting them to understand that e.g. no, "tidying up" the order of fields in a public structure you've published isn't safe back in the 1990s before they came to god and actually provided sane APIs which hide internal data structures.
Now, it's true that Hyrum's Law means any detectable change, even if it was never documented, will break somebody if there are enough people depending on your system. That's a big deal if you're the Linux kernel, or the HTTP/1.1 protocol, as it means even trivial "this can't break anything" fixes may break stuff. For example, as I understand it Google once broke search in Asia by changing an internal constant so that a hashmap would re-allocate (thus invalidating pointers to items in the map) slightly earlier. C++ code relying on pointers to just magically stay valid across inserts was completely wrong before they broke it, but anybody staring at a 500 page on google.com doesn't care why it broke they just want it fixed.
Most of us needn't much worry about Hyrum's law. That would be, as an old boss repeatedly told us, "A good problem to have" because it means you're having enormous impact.