[lldb-dev] Is there a way to inspect signaled stack?

Pavel Labath via lldb-dev lldb-dev at lists.llvm.org
Mon Nov 16 03:26:10 PST 2015

Hi Eugene,

the libc signal trampoline should have .eh_frame unwind info (I am
assuming this is x86_64 btw), and last time I looked at it, it seemed
that it should be able to handle sigaltstack(). However, I have never
tested this, so it's quite possible there is still some bug hidden
there. Could you file a bug with a small repro case and attach the
output of (thread backtrace) with logging enabled (log enable lldb
unwind). We'll try to look at it.


On 13 November 2015 at 19:22, Eugene Birukov via lldb-dev
<lldb-dev at lists.llvm.org> wrote:
> Hi,
> I am running on Ubuntu Linux. I am using a custom debugger built upon LLDB
> C++ API using version 3.7.
> The target program issues a lot of "legitimate" SIGSEGV signals that it
> handles itself. Its signal handler runs on a separate stack (it uses
> sigaltstack() and SA_ONSTACK). Now, sometimes a bug in the program causes
> SIGSEGV that the handler cannot deal with and it crashes. Now, when I load
> the core, I see stack frames for the signal handler stack, but what I really
> need are frames for the signaled stack.
> Of course, I have access to siginfo_t and ucontext_t, so I can try to use
> some unwind library, but that approach is far from ideal - the LLDB already
> has the unwinder. So, what should I do to get the set of SBFrame's that I
> can query about local variables, etc.? I mean, something like .cxr command
> in Windbg would be really handy...
> Thanks,
> Eugene
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