[libunwind] Basic use of dynamic features?

[Tommy Hoffner]

I'm trying to use libunwind together with dynamically generated code.

My main concern has been to have the following call-chain on the stack: 
c++-code -> dynamically generated code -> c++-code, where the last one 
does a throw that get caught on the other side of the dynamically 
generated code.

I made a small test that seems to work fine for UNW_LOCAL_ONLY. Due to 
debugging problems I've decided to add my own stackdump function (in my 
application source) that I could call from inside a debugger that lacks 
support for this libunwind.
Generalizing my test (e.g. removing UNW_LOCAL_ONLY and having a 
stackunwinder present in the code) forced me to link against 
libunwind-ia64, which in turn made my initial test fail (it only 
registers dynamically created unwind-info and uses throw and catch).
As I understood it UNW_LOCAL_ONLY limits the functionality to a pure 
subset of what you get otherwise. I also thought that using the same 
functionality in libunwind.so and libunwind-ia64.so would give me the 
same results as long as I'm only using the "local" functionality. Have I 
missinterpreted something basic here?

And yes, I can live with UNW_LOCAL_ONLY for my basic functionality but 
looking at writing my own stackdump function seems to force me to use 
remote features.
If I want to write my own stackdump function that I could call from the 
commandline in a debugger. I therefor need to get some kind of reference 
to the stack I want to dump. Calling a function from the command line in 
the debugger makes the calling function to be placed on another 
callstack than the application I want to debug. I'm not shure on exactly 
how it is implemented but functions like this can access the applicatons 
data so I assume the correlation between them (called function and the 
application I'm debugging) could be viewed as two threads (same data, 
different stacks).
Do I need remote functionality to be able to access another threads 
callstack (whitout it doing things like unw_local_init itself)?
Any tips on how to do it?

I'm still using libunwind 0.97, but will hopefully move to 0.98.2 any 
day now,

/Tommy

--
Tommy Hoffner
Senior Software Designer
Compiler Technology

Ericsson AB
Development Unit Core Network Development
Tel:    +46 13 23 57 12
Fax:    +46 13 23 57 99
address@hidden
www.ericsson.com

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