site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com On 22 Nov 2008, at 21:39, Terry Lambert wrote: Ok, I'll have a look. #include <signal.h> #include <stdio.h> #include <ucontext.h> #include <setjmp.h> // check whether we really caught the exception static int caught; static sigjmp_buf env; typedef void (*__sighandler_t)(); void install_signal_handler(int signo, __sighandler_t handler) { struct sigaction sa; sa.sa_handler = (void *)handler; sigemptyset(&sa.sa_mask); // needed for the ucontext parameter to be available sa.sa_flags = SA_SIGINFO; sigaction(signo, &sa, NULL); } int main() { double a, b; b = 0.0; asm volatile("mtfsfi 6,15"); // install the handler for SIGFPE install_signal_handler(SIGFPE, signal_handler); // trigger an exception caught = 0; if (!sigsetjmp(env,1)) { a = b/b; printf("Should never get here\n"); return 1; } else { printf("Returning from longjmp 1, caught signal: %d\n",caught); } if (!caught) return 1; return 0; } The output is (on a dual G5): $ gcc -o sig6 sig6.c $ ./sig6 Returning from longjmp 1, caught signal: 1 Should never get here $ sw_vers ProductName: Mac OS X ProductVersion: 10.5.5 BuildVersion: 9F33 Thanks, Jonas _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... On Nov 22, 2008, at 11:56 AM, Jonas Maebe <jonas.maebe@elis.ugent.be> wrote: [ ... ] @OSF_COPYRIGHT@ The base intent of strings of this format in source code us to cause source code control systems to insert/replace the text with source code known to the sccs at check-in time. Given that our current sccs checkin scripts do not reprocess a number of tag string like $Id:$ and this one, it would be my completely unofficial guess that the copyright boiler-plate for the file was copied from the corresponding x86 file, and that was left in accidently (_struct.h in x86 and ppc are new works by Ed, myself, and others as part of cleaning up namespace issues for UNIX conformance). Ok, thanks. I guess I'll have to go for installation time conversion in that case (unless sw licensing one day decides otherwise)... The official Apple position is a question best directed to DTS. I wish they (well, sw licensing) were as responsive and helpful as you are. My initial version used some form of (sig)longjmp instead of steps 5 to 7 to hand over control to our run time system, but that does not work for fpu exceptions (at least not on PPC). The reason was that as long as you did not return from a signal handler, fpu exceptions remained disabled (well, you could re-enable them in the fpscr, but the kernel dropped them on floor as soon as they occurred again afterwards). I can't immediately find again where this happens in xnu, but if you are interested I could try to look it up again. Please do; that was the specific intent of sigsetjmp/siglongjmp. Assuming the sigsetjmp happened prior to the signal handler, I would expect the mask state to be restored on siglongjmp. If it is not, I'd class that as a bug (NOTE: not a bug if you are using {set| long}jmp instead of sig{set|long}jmp). If you don't see this, please file a bug. Before I do so, here's a test program from 2004 I dug up that demonstrates the problem (ppc-specific) -- just to make sure that I didn't overlook anything: void signal_handler(int signum, siginfo_t *info, ucontext_t* sigcontext) { caught = 1; siglongjmp(env,1); } // trigger another exception caught = 0; if (!sigsetjmp(env,1)) { a = b/b; printf("Should never get here\n"); return 1; } else { printf("Returning from longjmp 2, caught another signal: %d \n",caught); } if (!caught) return 1; I'm not sure what alternatives I have to convert hardware/OS exceptions into language exceptions (at least not if I want to be able to provide backtraces to the consumers of those exceptions, like we do right now. You could always take and eat the Mach exception sent to your task, prior to it being converted into an AST and then into a signal. I admit I took the easy road until now and simply started off from a copy of the FreeBSD exception handling code we already have. Maybe I'll have to dig in Mach after all (until now I've been able to avoid that :) This email sent to site_archiver@lists.apple.com