[plt-scheme] MzTake - relative line numbers

From: Vadim Nasardinov (el-vadimo at comcast.net)
Date: Fri Aug 27 12:31:38 EDT 2004

On Tue, 2004-08-10 at 13:10, david.laffin at lineone.net wrote:
> I have just spent an hour or so playing with MzTake; it's seriously
> cool. However even in that short period of time, I found the fact
> that the absolute line and column locations of trace points have to
> be changed after even minor edits to the target text to be somewhat
> irritating.
> There must be a better way?

Moses DeJong[1] wrote a scriptable Tcl frontend[2] to GDB using
the GDB/MI interface[3].

He had this to say on the subject of fragile absolute breakpoints[1]:

  | Currently, breakpoints are set at a line number in a file, and the
  | line numbers need to be updated when the source file changes. It
  | is obvious that having to update line numbers in every regression
  | test after a change to the source code would be tedious and
  | error-prone. A simple solution to this problem is to create a new
  | type of breakpoint that contains a function name and an offset in
  | lines from the start of the function. In this way, a breakpoint
  | specification like {my_func + 5} could be given, the line number
  | of my_func could be queried, and the breakpoint could be set at
  | the returned line plus five. This would insulate breakpoints from
  | changes in the source file that shift a function up or down some
  | number of lines.

In and of itself, this is not a complete solution, but probably a
useful thing to add to MzTake.  This seems to be a hard problem
with no apparent solution.

(Mo's paper was mentioned by David N. Welton[4].)


  1. Scripted Debugging : Using Tcl and GDB to debug C code
  2. http://www.uncounted.org/tcl/gdbmi-0.1.tgz
  3. GDB/MI Command Description Format
  4. http://lambda-the-ultimate.org/node/view/179

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