The singlestep debugger works only with the engine
When you create a new word there’s often the need to check whether it
behaves correctly or not. You can do this by typing
badword. A debug session might look like this:
: badword 0 DO i . LOOP ; ok 2 dbg badword : badword Scanning code... Nesting debugger ready! 400D4738 8049BC4 0 -> [ 2 ] 00002 00000 400D4740 8049F68 DO -> [ 0 ] 400D4744 804A0C8 i -> [ 1 ] 00000 400D4748 400C5E60 . -> 0 [ 0 ] 400D474C 8049D0C LOOP -> [ 0 ] 400D4744 804A0C8 i -> [ 1 ] 00001 400D4748 400C5E60 . -> 1 [ 0 ] 400D474C 8049D0C LOOP -> [ 0 ] 400D4758 804B384 ; -> ok
Each line displayed is one step. You always have to hit return to
execute the next word that is displayed. If you don’t want to execute
the next word in a whole, you have to type n for
nest. Here is
an overview what keys are available:
Next; Execute the next word.
Nest; Single step through next word.
Unnest; Stop debugging and execute rest of word. If we got to this word with nest, continue debugging with the calling word.
Done; Stop debugging and execute rest.
Stop; Abort immediately.
Debugging large application with this mechanism is very difficult, because you have to nest very deeply into the program before the interesting part begins. This takes a lot of time.
To do it more directly put a
BREAK: command into your source code.
When program execution reaches
BREAK: the single step debugger is
invoked and you have all the features described above.
If you have more than one part to debug it is useful to know where the
program has stopped at the moment. You can do this by the
BREAK" string" command. This behaves like
BREAK: except that
string is typed out when the “breakpoint” is reached.
dbg( "name" – ) gforth-0.4 “dbg”
break:( – ) gforth-0.4 “break:”
break"( ’ccc"’ – ) gforth-0.4 “break"”