The following innocuous looking code generates a range check error:

{$R+}
function Count: qword;
begin
   Result := 0;
end;
var
   i: Integer;
begin
   for i := 0 to Count-1 do
     WriteLn(i);
end.

I can (more or less) see why, but it means that I can't (for example) compile the Cocoa widget set in 64 bit with bounds checking on, as then qword seems to be used as a count for, for example, NSarray.

Am I missing something?

Colin

C Western wrote

The following innocuous looking code generates a range check error:

The code shouldn't generate a range check error, as the target type is signed.

Note that Oberon was designed by Niklaus Wirth specifically to prevent this kind of problems. See the notes on type inclusion in section A.4.4 of An introduction to Oberon-2 <http://www.cs.bath.ac.uk/~claire/Oberon.pdf>

Apple has never heard of type inclusion or even range checking and is arbitrarily mixing signed and unsigned types.

Regards,

Adriaan van Os

Count returns Unsigned Qword.
unsigned $FFFFFFFFFFFFFFFF is beyond 32-bit boundary.

The similar issue, but more explicit.

{$R+}
function Count: qword;
begin
  Result := 0;
end;
var
  i: Integer;
  K : Qword;
begin
  K:=count-1;
  writeln(K);
  I:=k;  // <-- rangecheck error
  writeln(i);
end.

thanks,
Dmitry

Note that shifting the loop variable to Int64 still triggers the range check error. Using qword for the loop variable triggers an overflow error.

Apple has never heard of type inclusion or even range checking and is arbitrarily mixing signed and unsigned types.

I don't think this is an Apple issue - an unsigned type is not unreasonable for a count.

Colin

Integer is 32-bit, QWord is 64-bit. *Of course* there is a range check error then. You need to use e.g. SizeInt as counter variable type in those cases (SizeInt is 32-bit on 32-bit systems and 64-bit on 64-bit systems).

Regards,
Sven

 RangeCheckCount = objccategory(NSArray)
    function intcount: Integer; message 'intcount';
  end;

{ RangeCheckCount }

function RangeCheckCount.intcount: Integer;
begin
  Result:=Integer(count);
end;
var
  arr : NSArray;
  for i:=0 to arr.intcount-1 do

?

I changed the type used to evaluate for-loop bounds in ISO Pascal mode because of https://bugs.freepascal.org/view.php?id=24318 . Maybe the same should be done for other non-TP/Delphi modes too.

Jonas

Actually, it won't help because "qword - 1" will still be evaluated as qword. The issue is that there is no safe way to evaluate this with range checking that is correct in all cases without a 128 bit integer type:
1) if you evaluate it as qword, you get a range error if count is 0 (as above)
2) if you evaluate it as int64, then if count is high(int64)+1 you will get a range error even though the result could be represented in int64

In this particular case, because the counter is 32 bit (which seems quite unsafe for use with a container whose "count" property is 64 bit), using int64 would be "correct", but it's not a systemic solution (as shown above) and hence not something to implement in the language.

Jonas

Jonas

The actual code that triggered my interest was:

procedure LCLViewExtension.lclSetEnabled(AEnabled: Boolean);
var
   ns : NSArray;
   i  : integer;
   obj : NSObject;
begin
   ns := subviews;
   for i := 0 to ns.count - 1 do
   begin
     obj := NSObject(ns.objectAtIndex( i ));
     ... process obj ...
   end;
end;

I suppose i should be declared as the same type as ns.count which is NSUInteger = qword, but this will still trigger the error. You can avoid the problem by coding the loop as:

   for i := 1 to ns.count do
   begin
     obj := NSObject(ns.objectAtIndex( i-1 ));

so I suppose the real flaw is that the first item is at index 0, rather than 1, but I don't think that is a battle I am going to win.

Given how common the above bit of code is likely to be, I can't see any way of fixing this without some work in the compiler.

Colin

imho, bad approach to adjust compiler for not safe code. However, getting a compiler warning would be nice.

Some time ago, the compiler has been extended with for-in syntax:

var
  SubView : NSView;
begin
  for SubView in ns.subviews do
  begin
    .. process obj ...
  end

thanks,
Dmitry

On Sat, Jan 27, 2018 at 12:51 PM, Dmitry Boyarintsev <

That requires objectivec2 though
https://www.freepascal.org/docs-html/ref/refse76.html#x138-16000011.10 (min version is macOS 10.5)

thanks,
Dmitry

The problem is that count is qword, so the operation is qword until it needs to convert it

for i:=0 to integer(qword( qword(count) -  qword(1)) do

try this:

for i := 0 to *integer*(Count)-1 do

Without type inclusion, that is in a language that allows mixing typed an untyped numbers, there is no anambiguous solution, as Jonas points out. So, I suggest to choose the next best solution, which is to let result type of the expression decide whether to apply 1) or 2). In this case, it would be
2) as the result type is signed.

Regards,

Adriaan van Os