[metapost] bug in the label bbox

[Martin Budaj]

Hi,

when using numbersystems other than scaled, the following example
fails to calculate the bounding box of an empty label (MetaPost
version 2.00):

beginfig(1);
 path q;
 q:=bbox thelabel("",(0,0));
 message "BBOX: " & decimal xpart llcorner q & " " &
                    decimal ypart llcorner q & " " &
                    decimal xpart urcorner q & " " &
                    decimal ypart urcorner q;
endfig;
end

The results are:

scaled (OK, as bboxmargin is 2bp):
    BBOX: -2 -2 2 2
decimal:
    BBOX: -2 -1E+1000000 2 1E+1000000
binary:
    BBOX: -2 -9.999999999999999999999999999999999E+999999 2
9.999999999999999999999
999999999999E+999999
double:
    ! Arithmetic overflow.

Best regards
Martin