On Wed, 14 Feb 2018 20:26:01 +0100, Christof Warlich said: > record the build's dependencies. On subsequent runs of the build, these > depencencies could then be used to decide which compoments must be > rebuilt due to changed dependencies.
Doesn't "make" already do what you want? Oh, wait... > dependency recording, because the "results" of running "ls -l" do depend > on its shared libraries! This way lies madness - touch glibc or other package like that, and you just forced a rebuild of the entire world. In fact, I suspect that trying to follow "dependencies" to that level will result in build times close to what a 'make world' would do, because computing what ends up being the transitive closure of all file references is painful. Hint: To really do this correctly, you need to be able to force 100% code path coverage - otherwise you won't pick up the fact that /usr/lib64/libsnark.so is only actually used in an error path or similar rare-access corner case. For bonus points: openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_MONETARY", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MONETARY", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_TIME", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_TIME", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_NUMERIC", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_NUMERIC", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_CTYPE", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_CTYPE", O_RDONLY|O_CLOEXEC) = 3 Which file(s) count? How do you test for all values of $LANG and the various LC_* environment variables? There's a reason that most sane software builds and tools like rpm / dpkg and so on just check "glibc is still version 2.22" and don't bother going any further than that. And it just gets worse if you include kernel patches - how many modules end up involved in an open() call on a USB device? How do you detect that your code "depends" on a given behavior - often kernel patches address error conditions that doesn't change the perceived behavior in your userspace program... ... until a rare error condition arises. At this point, you need 100% code coverage of both the userspace *and* the kernel. To quote the movie Animal House: "My advice to you is to start drinking heavily....."
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