On Thu, Apr 14, 2011 at 2:10 PM, Paul Smith <psm...@gnu.org> wrote: > There is no specific region of the file that's locked: the lockfile is > basically a file-based, system-wide semaphore.
Yes, it's conceptually a semaphore. In fact a Windows port might prefer to use real semaphores. The reason I stayed away from them on the POSIX side is that, according to my reading, POSIX semaphores don't go away automatically when the creating process exits; they need to be explicitly released. Which entails a lot of responsibility and complexity in terms of signal handling and so on. An exclusive file lock produces the same result but goes away with its file descriptor. File locking is also older and thus likely a little more portable, though both are pretty old. > The entire file is [...] empty and has no content. That's not actually the case with the current implementation. The file can have content, in fact the obvious candidate is often the Makefile as shown in the test case. It must be writable according to fcntl locking semantics but it is never written to. > I'm not sure I like the idea of having to define a lockfile to enable > this feature though. It feels a little too much like exposing the > implementation details to the user. Agree. This needs a little more thought. David _______________________________________________ Bug-make mailing list Bug-make@gnu.org http://lists.gnu.org/mailman/listinfo/bug-make
