More about SwiftForth…

 

Overview

Forth Implementation Features

Optimizing Compiler

Programming Tools

Debugging Tools

SWOOP Object-Oriented Programming

Libraries, Functions, Callbacks, and Threads

Windows Programming

SwiftForth Programming References

Release History

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Debugging Tools

Disassembler and decompiler

SwiftForth includes a disassembler can be used to generate human-readable source code from compiled definitions. This is useful as a cross check, whenever a new definition fails to work as expected, and also shows the results of SwiftForth’s optimizing compiler. By disassembling a definition, you can see exactly what instructions were generated by the compiler.

The single command SEE <name> disassembles the code generated for name.

For example, the definition of TIMER is:

   : TIMER ( u -- )   COUNTER SWAP - U. ;

It disassembles as follows:

   SEE TIMER
   47170F   45B2AF ( COUNTER ) CALL        E89B9BFEFF
   471714   0 [EBP] EBX SUB                2B5D00
   471717   4 # EBP ADD                    83C504
   47171A   40916F ( U. ) JMP              E9507AF9FF

The left column shows the memory location being disassembled. This is followed by the instruction (or data) at that location. Note that the disassembler attempts to match named locations in memory with their addresses. The right column shows the actual bytes in memory.

Single-step debugger

A simple single-step debugger allows you to step through code compiled from a source file. Here is a simple example:

   [DEBUG
   : 2X ( n1 -- n2 )   DUP + ;
   : 3X ( n1 -- n2 )   DUP 2X + ;
   : 4X ( n1 -- n2 )   DUP 2X SWAP 2X + ;
   : 5X ( n1 -- n2 )   DUP 3X SWAP 2X + ;
   DEBUG]

Assuming this source has been compiled, you may type 4 DEBUG 5X to enter the single-step debug loop.

At each step, the source line is displayed with the next word to be stepped through highlighted. After this, the current data stack is displayed (in the familiar .S format) along with a prompt for the next step:

• Nest executes the next word, nesting if it is a call.
• Step executes the next word, with no nesting.
• Return executes to the end of the current (nested) definition without stopping.
• Finish executes to the end of the top-level definition without stopping.