[PicForth] Code generation bug with infinite loops, dead code, and 'else only' if constructs

[Alex Holden]

OK, this is a bit of an obscure one. I had many lines of code in an 
infinite loop in my main, and I wanted to quickly test something out 
without commenting out every line of the loop, so I added something like 
this at the beginning of main before the loop: dosomething begin again

The code picforth generated caused it to execute the 'dosomething' as 
expected but then it entered the main loop as normal as if the 'begin 
again' wasn't there. After a bit of messing about I seem to have 
discovered that the code generation bug is only triggered when there is 
an 'else only' if construct (ie. sometest if else dosomething then) 
inside the main loop. Here is some example code:

: fred ;
: barney ;
: sometest 0 ;
main : test
         fred begin again
         begin sometest if else barney then again
;

barney shouldn't get called but it does. Here's the generated code:

0x0000  018A    clrf    0x0A
0x0001  2809    goto    0x009   ; (init-picforth)
         ; name: fred
         ; max return-stack depth: 0
0x0004  0008    return
         ; name: barney
         ; max return-stack depth: 0
0x0005  0008    return
         ; name: sometest
         ; max return-stack depth: 0
0x0006  0384    decf    0x04,f
0x0007  0180    clrf    0x00
0x0008  0008    return
         ; name: (init-picforth)
         ; max return-stack depth: 0
0x0009  3032    movlw   0x32
0x000A  0084    movwf   0x04
         ; name: test
         ; max return-stack depth: 1
0x000B  2004    call    0x004   ; fred
0x000C  280E    goto    0x00E   ; test + 0x003
0x000D  2005    call    0x005   ; barney
0x000E  280D    goto    0x00D   ; test + 0x002

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