Error in 32 bit calulation

WEB TMS WEB Core
1

Hi Bruno

i am testing an encryption routine in webcore and get crazy results and/or exceptions.
Finally i could shrink the code to following example:



procedure test;
var a,b,c  : longword;              // or cardinal
begin
   a:=2654435769;                      // $9E3779B9
   b:=1147237152;                      // $44617320
   c:=a xor b;
end;



//   c should be  3663071897        $DA560A99

in a windows exe i see a correct result but not in webcore.
i tested with the internal debugger (in win64 and chrome).

following error is raised:

ERROR
Uncaught [object Object] | fMessage:: fHelpContext::0 
at http://localhost:8000/Login/Login.js [469:9]X


The Internal debugger in chrome sometime shows a crazy result:  

c=-631895399

But longwords or cardinal should always be positive !!!


Any idea ?

2
Attachment:

Error is raised because range check is on by   {$R+} in code.

Seems js code is working integer here.


You can see this in the debugger too.
C is shown as integer


procedure Tftest.WebButton1Click(Sender: TObject);
var 
   a,b,c,d : cardinal;         a = 2654435769,   b = 114723152,  c = -631895399,   d = 0

begin
   a:=2654435769;     a = 2654435769
   b:=1147237152;     b = 1147237152
   c:=a xor b;        c = -631895399

...

3

Attachment 2


Hi

There is a general problem with logical operations on 32 bit in webcore.

Try following:


{$R-}
procedure Tfanmeldung.WebButton1Click(Sender: TObject);
var
  x,y,a,b : longword;    x = 0, y = -2147483648, a = 2147483649, b = -2147483647

begin
//1
   x:=0;                        x = 0
   y:=$80000000;        y = -2147483648
   a:=y+1;                    a = 2147483649

//2
   y:=x or $80000000;   y = -2147483648, x = 0
   b:=y+1;                      b = -2147483647  

   a:=a;   // dummy
end;


Run this step by step with the internal debugger.

As you see a and b are different.
In case 1 y seems to be correct because a:=y+1 is calculated correct.
In case 2 y seems to be the same but b:=y+1 is different and wrong.
In both cases the debugger displays y as negativ.
Seems that logical operations like OR are treated as integer internally.





Please run the same example with {R+}:

{$R+}
procedure Tfanmeldung.WebButton2Click(Sender: TObject);
var
  x,y,a,b : longword;           x = 0, y = 2147483648, b = 0

begin
//1
   x:=0;                       x = 0
   y:=$80000000;       y = 2147483648
   a:=y+1;

//2
   y:=x or $80000000;
   b:=y+1;

   a:=a;   // dummy
end;

The debugger displays y as positiv !
a is not displayed (why?)  but you can see ist under Scope: a:=: 2147483649
which is correct.

y:=x or $80000000 creates a range check exception and execution is aborted.



4

We have asked the compiler engineers to investigate.

5

The compiler engineers made improvements in this area and this will be addressed in the next update of the compiler.