[fpc-devel] Bug 4004

[Colin Western]

Peter Vreman wrote:

>>Gerhard Scholz wrote:
>>    
>>
>>>The check for overflow is obviously implemented different in 2.0.0 and
>>>2.1.1
>>>      
>>>
>>I'm not sure, at least
>>
>>    
>>
>>>.L9:
>>>     movw %dx,-12(%ebp)
>>>.Ll3:
>>>      
>>>
>>suggests that the target is not an integer, but instead is a (possibly
>>unsigned) word type. Please check again!
>>
>>    
>>
>>>A solution would be to replace that line by:
>>>    d := integer(Ord(a))-Ord(b)
>>>
>>>It seems that the compiler now sees a "ord(c)" to be a BYTE, and BYTE -
>>>BYTE
>>>shall give a BYTE, and -1 is not in the range allowed for a BYTE.
>>>      
>>>
>>Differences always should be interpreted as signed values, the error
>>message IMO comes from the final assignment.
>>    
>>
>
>What with cardinal-cardinal and pointer-cardinal or pointer-byte? Those
>can't be represented by a longint (the native singed type of pascal). In
>2.0.0 the those were converted to int64 values, but users were complaining
>about the warnings that were generated.
>
For that matter Integer-Integer can't (in general) be represented by an 
Integer, which I suppose is why we have range checks. The documenation I 
can find is a little vague as to what the general result of +/- 
operations should be - it just seems to say integer which suggests that 
a difference between ordinals should be signed. (I think pointers are a 
slightly different case)

Colin