[darwin] unwind context question

[Andreas Tobler]

Geoffrey Keating wrote:

> Won't Darwin do this for you?  All you should need to do is catch SIGSEGV.

Well, not from my experience. I tried, but not success. Maybe I run a 
kernel which is to old? But I don't think so.

#include <stdio.h>
int main(int argc, char *argv[]) {
     printf("%d",*((int*)0));
     return 0;
}

[titanium:~/gcc-work/exception] andreast% ./print
Bus error

I write to a protected mem area.

[titanium:~/gcc-work/exception] andreast% gdb print
Program received signal EXC_BAD_ACCESS, Could not access memory.
0x00001db0 in main ()
(gdb)

So, these kind of errors end up in KERN_PROTECTION_FAILURE. And a 
SIGSEGV does not help. At least I didn't manage it to catch the failure.
It would be much easier to handle a SEGV than incorporate a mach msg 
handler.


>> Below the disass.
>> I would expect context->ra at 0x9000fae0 and not at 0x9000fa9c.
> 
> 
> Maybe.  It's hard to tell without seeing how the return address got 
> set.  You'll note that the code there does eventually wind up in sigreturn.
> 

What do you need to see?

Thanks,
Andreas