OpenEuphoria

Re: Interpreter erroneously reading some numbers

• Posted by petelomax Jan 24, 2015
• 1489 views

That exact problem is on my radar, not sure how to proceed. When a 32-bit compiler is trying to construct a 64-bit executable, I'd like #8000000000000001 to yield {#80000000,#00000001} (or {lo_dword,hi_dword}) and something similar for 80-bit floats, and when a 32-bit compiler is constructing a 32-bit executable, I'd like ^warning: precision loss messages for such values. Of course, #8000000000000000 is fine as-is, it is not so much a matter of counting digits but explicitly testing for precision loss.

For what it is worth, which is probably not very much at all, and this is bytes->value not source->bytes, in my filedump.exw program I resorted to this:

constant atom h8a = allocate(8), 
         integer h8i = floor(h8a/4)     -- (easier for ilASM) 
 
function reconstitute_int64(sequence s8) 
-- While 64-bit apps use 80-bit floats, which have 64 bits of precision, 
--  32-bit apps use 64-bit floats, which only have 53 bits of precision. 
-- This retrieves "normal" numbers as "normal" values (eg 0,1,-1,237), 
--  but eg #8000000000000001 (or more accurately {1,0,0,0,0,0,0,#80}), 
--  rather than minus the 1, as {#80000000,1}, ie {hi_dword,lo_dword}. 
-- (If invoked on 64-bit, does a pointless peek and returns an atom.) 
object res 
    poke(h8a,s8) 
    #ilASM{  
        [32] 
            mov eax,[h8i] 
            lea edi,[res] 
            fild qword[ebx+eax*4] 
            call %opMovbi               -- call StoreFlt ([edi]:=ST0) 
            mov eax,[res] 
            mov edi,[h8i] 
            cmp eax,h4 
            jl %opRetf 
            fld qword[ebx+eax*4] 
            fistp qword[ebx+edi*4] 
        [64] 
            mov rax,[h8i] 
            lea rdi,[res] 
            fild qword[rbx+rax*4] 
            call %opMovbi               -- call StoreFlt ([rdi]:=ST0) 
        [] 
          } 
    if peek({h8a,8})=s8 then 
        return res 
    end if 
    poke(h8a,s8) 
    return reverse(peek4u({h8a,2})) 
end function 

Pete