Re: GCJ Stack Traces for arm-wince-pe on gcj 3.4.3

[Andrew Haley <aph at redhat dot com>]

Craig Vanderborgh wrote:

> We have been busy bringing up gcj 3.4.3 on arm-wince-pe (Windows CE 5
> and 6).  At this point everything is pretty much working (garbage
> collection, hash synchronization, reflection, class loading, etc.) on
> real-world GCJ applications.
> 
> What we are still lacking (and have always lacked..) is stack traces.
> I understand that some work has been done in the most recent versions
> to implement an arm-elf unwinder that supposedly works and that stack
> traces are available now, at least for arm-elf-linux.  We considered
> porting this (gcc-4.1.1) and using this version of gcj, but the
> classpath-based libgcj is too big for us to handle on WinCE embedded
> systems.  That's one reason why we're going for gcc-3.4.3.

Fair enough, if it does what you need.

> What could we do to implement stack traces on gcc-3.4.3?  What would
> be the best approach?  One idea we're considering is to alter the code
> generation in gcc/gcj so that the ARM function calls adhere to a
> simpler (unwindable) format.  It seems like this would be the least
> invasive approach, since we then could continue to use SJLJ exceptions
> in gcj.  Is this the best approach, or would it be possible/prudent to
> backport the ARM unwinder from gcc-4.1.1+?

According to svn log, I added the ARM EABI backtrace on 2007-08-08.
It is not present in any gcc release before 4.3.0.

As I understand it, gcc-3.4.3 should be perfectly capable of generating
APCS-compatible code that has a stack chain you can unwind.  The only
problem you'll have is converting a code address to the handle of a
class.

Andrew.