To initialize an array, negative values can not be specified (see error
below).
Type casting to positive works, if you have the exact bit-size-matching
unsigned type.
If the typecast is to big, it also gives a range check.
But with $R- values that are to big, are truncated.
Except in bitpacked arrays.
- no range check error (that may be due to the sub range type ??)
- values to big, overwrite the neighbouring element
I think the latter is a bug. *If* the compiler accepts the value, then
it should protect neighbouring elements.
So is this a bug?
What should happen?
Doing
gcBitPackTinyNegArray[1] := cardinal(-1);
at runtime seems to work fine. (gives a compile time warning too / $R-)
program test;
{$R-}
type
TTinyNegRange = -2..3;
TBitPackTinyNegArray = bitpacked array [0..3] of TTinyNegRange;
TTestArray = bitpacked array [0..3] of byte;
const
// Warning: range check error while evaluating constants (4294967294
must be between 0 and 255)
// Works with $R-
// gcBitPackTinyNegArray : TTestArray = (2, cardinal(-2), 0,
cardinal(-1));
//Error: range check error while evaluating constants (-2 must be
between 0 and 18446744073709551615)//
//Also range check, even with $R-
// gcBitPackTinyNegArray : TBitPackTinyNegArray = (2, -2, 0, -1);
// No Error / WRONG Value, prints: 2, -2, -1, -1 // 0 is replaced by -1
// same with $R-
gcBitPackTinyNegArray : TBitPackTinyNegArray = (2, cardinal(-2), 0,
cardinal(-1));
// works
// gcBitPackTinyNegArray : TBitPackTinyNegArray = (2, 6, 0, cardinal(-1));
// gcBitPackTinyNegArray : TBitPackTinyNegArray = (2, 6, 0, 7);
begin
writeln(gcBitPackTinyNegArray[0]);
writeln(gcBitPackTinyNegArray[1]);
writeln(gcBitPackTinyNegArray[2]);
writeln(gcBitPackTinyNegArray[3]);
readln();
end.
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