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Re: Catching signal errors

Matt Watson wrote:

void fatalSigHandler(int sig, siginfo_t* info, void* context)
{
// We are very limited in what we are allowed to do in a signal handler. // Memory should not be allocated, and most libc functions should not be used.
static char sig_message[] = "Aborting: Fatal signal occurred!\n";

   write(1, sig_message, sizeof(sig_message));
   exit(1);
}


Never call exit() from a signal handler. You want _Exit() instead. exit() will call atexit() handlers which will are likely not signal-safe. And you probably want to use fd 2 (stderr), instead of fd 1 in the write() call.


Good suggestions. That's especially important when using dlopen or NSLinkModule on libraries. They could cause further signals or even signal deadlocks when they get unloaded.


That said: if you're not going to add any more info in your signal handler, or do any cleanup like unlink() files, it may just be best to let it crash and generate a crash log.


I assumed that he'd replace the handler with something else.

One of the handlers I have for a project calls execv() to restart the daemon in case of a crash. That is after writing errors to a log and closing open file handles/resetting signal masks (as they are both inherited by the new process), and doing some other general cleanup of the daemon's lock/state files.

-Kevin-
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References: 
 >Catching signal errors (From: Rick Steele <email@hidden>)
 >Re: Catching signal errors (From: Kevin Harris <email@hidden>)
 >Re: Catching signal errors (From: Matt Watson <email@hidden>)



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