[lldb-dev] Use lldb.so to create stack trace

[David Jones]

This works if all you want to do is print the stack trace.

However, if you wish to examine or modify the trace in ANY WAY, then LLVM's
printStackTrace() is no longer sufficient.

In my case, my language mangles names in its own way, because it is not
C++. I need to demangle these names, and therefore need to examine/modify
the output.

Right now I am forking, launching LLDB in the parent, and attaching to my
compiler in the child, and when LLDB gets notified of a signal, I print the
stack trace. This is essentially what the OP wanted. This works, but there
is a pause at startup while LLDB does??? (I think it's loading symbols).
I'd like to get rid of that pause, but have found no workable way of doing
so.

One idea I had was to have LLDB launch only after my signal handler has
caught a signal. Alas, in this mode, LLDB could not backtrace past the
signal handler  - all stack frames from my compiled code were dropped, so
that it looked like the code that generated the signal was in fact my
runtime.


On Tue, Jul 28, 2015 at 1:13 AM, Zachary Turner <zturner at google.com> wrote:

> Instead of linking lldb.so, which is basically an entire debugger, maybe
> you could just link llvm?  I don't remember which library has the stack
> trace function in llvm, but the function I believe is called
> llvm::sys::printStackTrace().  This will give you a much smaller overhead
> than bringing in all of lldb unnecessarily.
>
> On Mon, Jul 27, 2015 at 10:12 PM Schlottke-Lakemper, Michael <
> m.schlottke-lakemper at aia.rwth-aachen.de> wrote:
>
>> Hi folks,
>>
>> We are looking for a way to use lldb.so to print out a stack trace
>> programmatically. In our scientific simulation tool (written in C++) ,  we
>> use a custom terminate function where we are already able to print stack
>> traces in case of an abnormal abort, which uses some gcc-specific magic.
>>
>> My idea is to link our tool to lldb.so when compiling for debugging and
>> to use the library to print a stack trace programmatically, including
>> demangled names and correct line numbers. However, I don't really know how
>> to start thus I am wondering
>>
>> - has someone here done or seen something like this before?
>> - is there a tutorial for linking to lldb.so and making use of it through
>> C++?
>> - would this also work when compiling with other compilers than clang?
>>
>> Any help or pointers to relevant projects/documentation etc is greatly
>> appreciated!
>>
>> Regards,
>>
>> Michael
>>
>> --
>> Michael Schlottke-Lakemper
>>
>> SimLab Highly Scalable Fluids & Solids Engineering
>> Jülich Aachen Research Alliance (JARA-HPC)
>> RWTH Aachen University
>>
>> Wüllnerstraße 5a
>> 52062 Aachen
>> Germany
>>
>> Phone: +49 (241) 80 95188
>> Fax: +49 (241) 80 92257
>> Mail: m.schlottke-lakemper at aia.rwth-aachen.de
>> Web: http://www.jara.org/jara-hpc
>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.jara.org_jara-2Dhpc&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=DDUMf06MYELAe1Nlv7KChiwJLLHbYha4jtK_AOiWqwQ&m=xVT0HkfeqC08Qoa93HzeQ55AmpxQb4Ecvst4ybPmxRU&s=quSM9W4gQgTeWyTwz1wYwFfT6z6UhfjDndUcvvpCeAs&e=>
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