[fpc-pascal] TFileStream.SetSize sometimes fails

Michael Van Canneyt michael at freepascal.org
Fri Aug 14 20:42:49 CEST 2009

On Fri, 14 Aug 2009, Martin wrote:

> Michael Van Canneyt wrote:
>> On Fri, 14 Aug 2009, Martin wrote:
>>> However in c I can specify
>>>  open(fname, O_WRONLY | O_TRUNC );
>>> which does work (bypasses the bug)
>>> I haven't seen an equvivalent to O_TRUNC in fpc ?
>> Sure there is:
>> uses baseunix;
>> Var
>>   H : integer;
>> begin
>>   h:=fpOpen(fname,O_WrOnly or o_trunk)
>> end.
>> But that is not relevant:
>> a) FPC itself should not work around kernel/vbox bugs.
>> b) It would not help in Mattias' case anyway...
> I never said FPC should workaround, and I am not in favour for the Lazarus to 
> do so.
> Then again, if that had been a cross platform argument, there would be no 
> reason (IMHO) why lazarus could not set the flag , when opening the file. If 
> it had been cross-platform....

Windows has TRUNCATE_EXISTING, so in theory we could introduce fmTruncate to be
used in conjunction with fmOpenwrite, and then Mattias could use it in the TFileStream 

(As a side node: TRUNCATE_EXISTING also had/has bug when working on remote
files, you can find this in Microsofts Knowledge Base ;-))


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