(gawk.info.gz) Debugging Terms

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 14.1.2 Additional Debugging Concepts
 ------------------------------------
 
 Before diving in to the details, we need to introduce several important
 concepts that apply to just about all debuggers, including `dgawk'.
 The following list defines terms used throughout the rest of this
 major node.
 
 "Stack Frame"
      Programs generally call functions during the course of their
      execution.  One function can call another, or a function can call
      itself (recursion).  You can view the chain of called functions
      (main program calls A, which calls B, which calls C), as a stack
      of executing functions: the currently running function is the
      topmost one on the stack, and when it finishes (returns), the next
      one down then becomes the active function.  Such a stack is termed
      a "call stack".
 
      For each function on the call stack, the system maintains a data
      area that contains the function's parameters, local variables, and
      return value, as well as any other "bookkeeping" information
      needed to manage the call stack.  This data area is termed a
      "stack frame".
 
      `gawk' also follows this model, and `dgawk' gives you access to
      the call stack and to each stack frame. You can see the call
      stack, as well as from where each function on the stack was
      invoked. Commands that print the call stack print information about
      each stack frame (as detailed later on).
 
 "Breakpoint"
      During debugging, you often wish to let the program run until it
      reaches a certain point, and then continue execution from there one
      statement (or instruction) at a time.  The way to do this is to set
      a "breakpoint" within the program.  A breakpoint is where the
      execution of the program should break off (stop), so that you can
      take over control of the program's execution.  You can add and
      remove as many breakpoints as you like.
 
 "Watchpoint"
      A watchpoint is similar to a breakpoint.  The difference is that
      breakpoints are oriented around the code: stop when a certain
      point in the code is reached.  A watchpoint, however, specifies
      that program execution should stop when a _data value_ is changed.
      This is useful, since sometimes it happens that a variable
      receives an erroneous value, and it's hard to track down where
      this happens just by looking at the code.  By using a watchpoint,
      you can stop whenever a variable is assigned to, and usually find
      the errant code quite quickly.
 

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