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More fun with file descriptorsMore fun with file descriptorsPosted Jun 14, 2007 14:52 UTC (Thu) by davecb (subscriber, #1574)In reply to: More fun with file descriptors by nix Parent article: More fun with file descriptors
Hmmn, any app writer who kills his own syslog get exactly what
Joking aside, the code snippit was from a LD_PRELOAD library that
I suspect normal evolution will prune out the exceptions over
--dave
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More fun with file descriptors Posted Jun 14, 2007 18:24 UTC (Thu) by vmole (guest, #111) [Link] Hmmn, any app writer who kills his own syslog get exactly what they deserve (;-)) Any syslog that allows the user app to kill it through normal standard procedures (e.g. closing fds for a daemon) is broken. :-) Unfortunately, this is one of those cases where you have to know something about the underlying libc implementation to avoid screwing yourself. In particular, most of the implementations I've worked with only break if you've called openlog().
More fun with file descriptors Posted Jun 15, 2007 19:12 UTC (Fri) by giraffedata (subscriber, #1954) [Link] Any syslog that allows the user app to kill it through normal standard procedures (e.g. closing fds for a daemon) is broken. :-) It's not that you have to know the underlying libc implementation. Rather, you have to know libc's requirements of its environment. You don't leave a file descriptor open because you know syslog functions use it; you leave it open because the syslog facility requires you not to mess with any file descriptor you didn't create. There are dozens of ways a library places requirements on its environment because of resources shared among all code in the process. Some of the requirements are easily accepted, such as that a caller should not write over any memory it did not allocate (which allows the library to keep memory of its own). Sometimes the requirements are onerous, but "broken" is too strong a word for a library with inconvenient requirements. "less useful" or "dangerous" are better descriptions. Signal handlers, alarms, environment variables, stack space, terminal display space, Standard Error file contents, etc. are all controversial.
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