Date: Sun, 18 Jul 1999 14:13:02 -0500 (EST) From: Alfred Perlstein <bright@rush.net> To: Dag-Erling Smorgrav <des@flood.ping.uio.no> Cc: hackers@FreeBSD.ORG Subject: Re: Determining the return address Message-ID: <Pine.BSF.3.96.990718140958.14320g-100000@cygnus.rush.net> In-Reply-To: <xzpaesunsmw.fsf@flood.ping.uio.no>
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On 18 Jul 1999, Dag-Erling Smorgrav wrote: > Alfred Perlstein <bright@rush.net> writes: > > This looks like what you are doing is trying to grab the data on the > > stack before "log" which is the return address. > > Yes. It actually works :) > > > I doubt this is > > at all portable and may fail because of optimizations and ABI, such > > as archs that store the return address in a register... > > I know - I don't expect it to be portable. *slap* :) > > > gdb and glibc have some functions to assist in runtime backtraces, > > perhaps a look there may help? > > I found out about __builtin_return_address(0). what is that? a function? available on freebsd? > > > > BTW, is dladdr() signal-safe? > > not according to the sigaction man page. > > OK, is there any way I can find out that I am being called from a > signal handler, other than using a global variable? I want my logging > functions to be signal-safe - that's why I use writev(), and I've gone > to great lengths to ensure that log_makedate() (which uses > localtime_r() and strftime() to build a date string) and lvformat() (a > printf() clone with some additional goodies) are signal-safe. sigaltstack() ? If oss is non-zero, the current signal stack state is returned. The ss_flags field will contain the value SS_ONSTACK if the process is cur- rently on a signal stack and SS_DISABLE if the signal stack is currently disabled. by setting an alternate signal stack i think you can check if you are in a signal using this. this may not be the best way but it seems like a viable solution. -Alfred To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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