[armedbear-devel] [REVISED] Patch for including relevant java stack frames

[Tobias C. Rittweiler]

Mark Evenson writes:

> Attached is a revised patch incorporating Java stack frames in the
> backtrace against ABCL SVN HEAD.
>
> This revision:
>
> *  solves the "off by one" error of Tobias's original patch in a way
> that is more robust to stack dumps from other sources (such as calling
> into ABCL when the top level interpreter has not been established)
>
> *  restores the ability to inspect a mixed Java/Lisp backtrace via the
> ABCL inspector
>
> *  utilizes the stack optimization introduced by Erik in [svn r12064]
> in using a link in the StackFrame itself
>
> The Java stack traces certainly give an ABCL implementer a lot more
> useful information to understand what is going on although it could be
> more complete with information on the local variables on the various
> Java frames.  But I wonder how useful this would really be for the
> "end-user" who would be confused by the abstraction barrier ("Why am I
> getting reference to a Java stack in my Lisp call?").
>
> Comments please on whether this functionality would be useful, and
> potential improvements.

a) Why did you change SYS:BACKTRACE-AS-LIST to listify the frames? I
   deliberately changed it to return a list of StackFrame objects, so
   higher levels can decide whether they want to print java frames, or
   not. (Which addresses your concern about "abstraction barrier".)

   Perhaps because the name BACKTRACE-AS-LIST could be understand to do
   implicit listification? I could follow that line. In fact, I'd have
   liked to perform the following renamings, but opted out to change too
   many things with my patch:

      Rename BACKTRACE to PRINT-BACKTRACE

      Define BACKTRACE to return a list of StackFrames.

      Define BACKTRACE-AS-LIST to return a list of listified stack
      frames.

b) I don't like that 

      (frame-to-list #<JAVA-STACK-FRAME>) => ("class.meth(file.java:NN)")

   I think it should return ("class.meth" :file "file.java" :line NN) so
   higher levels can use that information. (For example `v' in SLDB.)

c) PRINT-FRAME contains an IGNORE-ERRORS which purpose I don't
   understand. Mind you, you actually copied that from my patch, so it's
   all my fault---I just can't remember why I put it in there. Do you
   know? If so, please add a comment.

  -T.