[fpc-pascal] File region locking unde Linux

[ajv]

Dear Jonas Maebe,

Thank you very much for the research you have done on this subject.
I was unaware of the power of strace, I have never used this 
application, I will go into it.
I see your name in the referred bug, I think you are the maintainer of 
this subject?
Do I have to report this as a bug or is it included in the mentioned bug?

Best regards, Anthony Vogelaar

==================================================================

Jonas Maebe wrote:
>
> On 03 May 2009, at 14:51, Jonas Maebe wrote:
>
>> On 03 May 2009, at 14:09, ajv wrote:
>>
>>> With Region Do                         Begin
>>>   l_type  := F_WRLCK; l_whence := SEEK_SET;
>>>   l_start := 10;      l_len    := 20
>>> End;
>>> If FpFcntl (F, F_SETLK, Region) = -1 Then
>>>   WriteLn ('unable to apply writelock');   //  <-- OK
>>> Sleep (20000);                              // Sleep 20 Sec
>>> FpClose (F);
>>> End.
>>> -------------------------------------------------------------------------------------- 
>>>
>>> Then within 20 seconds i start test to obtain a readlock on 80.
>>> This fails. Why? What am I doing wrong?
>>
>> Your test works fine under Solaris. It's a bug somewhere in the FPC 
>> Linux units. strace shows this for your first program:
>>
>> fcntl(3, F_SETLK, {type=F_WRLCK, whence=SEEK_SET, start=10, len=0}) = 0
>>
>> As you can see, "len=0" is passed to the system call (instead of 
>> len=20), so it locks the entire file. That's the reason why the other 
>> program is unable to lock anything else.
>
> It's similar to http://bugs.freepascal.org/view.php?id=13363 : the 
> kernel's off_t is 32 bit on 32 bit systems. It's defined as 64 bit in 
> the Linux rtl for all platforms.
>
>
> Jonas
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>