Re: [Amforth-devel] [bug] missing "then" not caught by compiler

[Kalus M. <mic...@on...>]

Hi Erich.

Its more like "keep it simple".

Tiny microprocessor forth systems usualy dont abort unstructured code.
For example in fig forth or Rockwell AIM65 Forth the ;s just  
returned, no error checking at all:

aim65:
code: ;S  ( IP <-- RP )
PLA
STA 9F
PLA
STA A0
JMP NEXT

fig forth entsprechend, zB. 8086:
code: ;S
MOV SI,[BP]  ( IP <-- R1 )
INC BP
INC BP
JMP NEXT


And amforth does not check for it too:
: ';'  compile exit [ ;


Big Forth systems do abort compilation if code ist unstructured. This  
is done by setting local variables which are checked by ; finaly.

Use depth of stack as a minor check. If stack depth has changed after  
compilation of a word look twice what was done there. So if you find  
a bad definition, enclose it in DEPTH and if it does not read 0 1  
like in
  depth : test 1 2 3 . . . ; depth .s <2> 0 1  ok
revise code.


Michael





Am 31.03.2009 um 20:56 schrieb Erich Waelde:

> Hello,
>
> amforth, rev.736 (3.4)
>
>
> amforth 3.4 ATmega32 ok
> > : test1 0= if -1  ( no then ) ;
>  ok
> > : test2 0= if -1 else 0 ( no then ) ;
>  ok
> > 1 test1 .
> --- hangs here until reset ---
> amforth 3.4 ATmega32
> > 1 test2 .
>  ?? -13 8
> >
>
> if statements missing the trailing "then" will compile
> without the compiler barking. I consider this a bug.
>
> calling such a word will produce a "hang" in one case.
> This can be viewed as another bug, but that is not
> important. In the other case it is producing an
> error message at least.
>
> Cheers,
> Erich
>