On Sun, 11 Sep 2016, Martok wrote:
Hi,
yes, I can confirm this as an overflow, but on its own, it should be safe. Above
430MB, the stream doesn't grow by a quarter but just by however much was
requested, luckily the branch fails before the wrong capacity could be set.
Test:
type
TMS2 = class(TMemoryStream) end;
var
ms: TMS2;
ds: Int64;
begin
ds:= 100*1000*1000;
ms:= TMS2.Create;
ms.SetSize(ds);
WriteLn(ds:15,' ', ms.Size:15, ' ', ms.Capacity:15);
inc(ds, ds div 10); // grow by less than 25%
ms.SetSize(ds);
WriteLn(ds:15,' ', ms.Size:15, ' ', ms.Capacity:15);
end.
with ds=100M, prints:
100000000 100000000 100003840
110000000 110000000 125005824 << grew by 1/4*100M
with ds=500M, prints:
500000000 500000000 500002816
550000000 550000000 550002688 << bug, grew by 1/10*500M
Output on linux 64-bit
cadwal: >tms
100000000 100000000 100003840
110000000 110000000 125005824
cadwal: >tms
500000000 500000000 500002816
550000000 550000000 625004544 This is 1/4
cadwal: >tms
869000000 869000000 869003264
955900000 955900000 1086255104
So it looks like a 32 vs. 64 bit issue.
from the method Realloc :
NewCapacity := (5*FCapacity) div 4; // 5*FCapacity can cause overflow
Changing this to
NewCapacity:=FCapacity + (FCapacity div 4)
Will probably fix the issue.
Michael.
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