[libunwind] unwinding undescribed frames

[Mark Young]

Our digital simulation application generates and executes code 
dynamically. This code is called from and makes calls to other C 
functions. We have need to unwind down to stack frames of our own 
creation which do not have unwind descriptors and also to unwind through 
relocated stack and register backing store. Most of our needs appear to 
be met by the proposed unw_init_remote routine with accessor functions 
identified by the unw_accessors_t structure.

It would help if the acquire_unwind_info accessor function could return 
some specific error code to terminate unwinding and cause a graceful and 
silent return from unw_step, preferably passing along that same error 
code. In our case this would be used when the ip passed to 
acquire_unwind_info falls in our dynamically generated code. We can 
handle unwinding through our undescribed frames and then restart the 
unwinder if a C function frame is reached. It would be nice not to have 
to use setjmp/longjmp to exit the unwinder as is presently necessary in 
the HP-UX ia64 unwind library implementation.

Also I suggest that the application-specific data arg in the 
unw_accessors_t structure be passed to the acquire_unwind_info and 
release_unwind_info functions as it is for the access_mem, access_reg, 
access_fpreg, and resume functions. Wrapper functions could be added if 
necessary to drop the argument to call existing external routines.

Thanks!
--Mark

--
Mark Young            address@hidden     Tel: 503.526.1661
Staff Engineer         www.model.com      Fax: 503.526.5473
Model Technology, Inc.
10450 SW Nimbus Avenue/Bldg RB, Portland, OR 97223-4347 USA