[PicForth] Code generation bug involving exit followed by if

[Alex Holden]

I was trying to track down where my program was going insane (haven't 
got to the bottom of that yet), and in order to figure out if it was 
somewhere in a particular word I inserted an 'exit' at the beginning of 
it, thereby turning the rest of the word into dead-code which should 
never execute. Surprisingly the exit seemed to be ignored and the rest 
of the word executed anyway. I've distilled it down to this example:

: sometest 1 ;
: dosomething ;
: unreachable ;
main : test exit sometest if dosomething then unreachable ;

Everything after the 'exit' should not execute, and 'unreachable' is, 
well, unreachable, right? Here's the generated assembly:

0x0000  018A    clrf    0x0A
0x0001  280A    goto    0x00A   ; (init-picforth)
         ; name: sometest
         ; max return-stack depth: 0
0x0004  3001    movlw   0x01
0x0005  0384    decf    0x04,f
0x0006  0080    movwf   0x00
0x0007  0008    return
         ; name: dosomething
         ; max return-stack depth: 0
0x0008  0008    return
         ; name: unreachable
         ; max return-stack depth: 0
0x0009  0008    return
         ; name: (init-picforth)
         ; max return-stack depth: 0
0x000A  3032    movlw   0x32
0x000B  0084    movwf   0x04
         ; name: test
         ; max return-stack depth: 0
0x000C  280D    goto    0x00D   ; test + 0x001
0x000D  2809    goto    0x009   ; unreachable

I wonder if this might somehow be related to the 'dead code getting 
executed' bug I reported on the 29th of November? I don't think that one 
has been fixed yet.

-- 
------------ Alex Holden - http://www.linuxhacker.org ------------
If it doesn't work, you're not hitting it with a big enough hammer