Date: Thu, 30 Oct 2008 09:34:25 -0400 From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> To: admin@cpcnw.co.uk Cc: freebsd-questions@freebsd.org Subject: Re: Seg Fault Action! Message-ID: <44y706qk9q.fsf@be-well.ilk.org> In-Reply-To: <op.ujqaapi3t4j7n6@3bsd.cpcnw.co.uk> (Graham Bentley's message of "Tue\, 28 Oct 2008 09\:36\:15 -0000") References: <20081027184022.14D9D10656C1@hub.freebsd.org> <op.ujqaapi3t4j7n6@3bsd.cpcnw.co.uk>
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"Graham Bentley" <admin@cpcnw.co.uk> writes: > I have often wondered what to do if I compile a port and > immediatly after trying to run it I get a seg fault. > > In the past I have just tried to find an alternative port > that did the same job, but it has always felt as though I > wasnt trying hard enough. > > Yesterday after upgrading all my ports tree I decided to > get printing working and cups / HP stuff all works fine > as does the web gui to cups so I decided to try and > make xpp. > > The result is 'Segmentation Fault' - thats it! > > How do I go about finding out what caused it and how to > get the program running? > > Any tips etc appreciated! Segmentation fault means (roughly) accessing a region of memory that hadn't even been mapped into that process. Generally you need some software debugging skills to go after these problems directly. There are some less direct steps you can take that can help. For one, make sure your ports are up-to-date with your installed ports tree before installing more ports. You can run the program under truss(1), which will help you figure out what kind of bad data is being passed to system calls (assuming that's where the failure is, but it's not unusual for that to be the case). You can generate a crash dump of the program, and (you or someone else) can use a debugger to see where it was when it failed -- usually a strong hint. And of course, asking for help in figuring out a specific problem is an option as well. I'd look at xpp, but at the moment my machines with the ports collection installed are powered down... -- Lowell Gilbert, embedded/networking software engineer, Boston area http://be-well.ilk.org/~lowell/
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