(+LOOP) should use the carry or overflow flag, not the sign bit about beetle

[apt1002]

The GForth implementation implements it like this:

Cell olddiff = n1-nlimit;
n2=n1+n;	
if (((olddiff^(olddiff+n))    /* the limit is not crossed */
     &(olddiff^n))	       /* OR it is a wrap-around effect */
    >=0) { /* & is used to avoid having two branches for gforth-native */
{ ... }

I can understand this by separately deoptimising the n>=0 and n<0 cases:

Cell olddiff = n1-nlimit;
n2=n1+n;	
Cell newdiff = n2-nlimit;
if ((n >= 0) ? (
    olddiff < 0 && newdiff >=0
) : (
    olddiff >=0 && newdiff < 0
)) { ... }

In other words, we exit the loop if olddiff and newdiff have opposite sign and olddiff and n have opposite sign.

[rrthomas]

Submit a patch to gforth based on the above, which replaces the comment "check this thoroughly", and removes the comment about defunct gforth-native.