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Re: Catching signal errors
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Re: Catching signal errors



Rick Steele wrote:


Forgive the ignorance but,

if one has a function like this within an application:


void SumFunction(){

Ptr pPtr = -1L; //create something that will obviously crash if deferenced
char pSomethingElse;
pSomethingElse = (*pPtr); // Causing the error
}


how would some one catch the signal that would inevitable occur so the app might be able to close down gracefully?

Try 0 (or NULL) -- it should cause a SIGSEGV or SIGBUS (depending on the platform), whereas -1L could (potentially) be a valid chunk of memory.


How about this snippet:
--------------------------------
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>

typedef void (*full_sighandler_t)(int,siginfo_t*,void*);

void installSignalHandler(int sig, full_sighandler_t handler)
{
   struct sigaction temp;
   sigaction(sig, 0, &temp);
   // Set the SA_SIGINFO flag so that sa_sigaction may be safely used.
   temp.sa_flags = SA_SIGINFO;
   temp.sa_sigaction = handler;
   sigemptyset(&temp.sa_mask);
   sigaction(sig, &temp, NULL);
}

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);
}

int main(int argc, char** argv)
{
   installSignalHandler(SIGSEGV, &fatalSigHandler);
   installSignalHandler(SIGBUS, &fatalSigHandler);

   int* foo = NULL;

   *foo = 0;

   exit(0);
}
--------------------------------
You should read the man pages for signal and sigaction.

-Kevin-

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 >Catching signal errors (From: Rick Steele <email@hidden>)



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