How can I catch this Error or check to nil?

[SunyD]

Hello,
i have following code from 3rd part:

Code: Pascal  [Select][+][-]

1. {$MODE DELPHI } // <--- it is compiled with Delphi-Mode
2.  
3. // PDataSetRecInfo ist Pointer to Record TDataSetRecInfo
4. // aBuffer is PChar
5. // dsRecInfoOfs is Integer;
6. //..
7.         with PDataSetRecInfo(aBuffer + dsRecInfoOfs)^ do begin
8.           riBookmarkFlag := bfCurrent;                       //sometimes error here
9.           riRecNo := 0;
10.         end;
11. //..
12.  

Sometimes the programm crashs with Errorcode:
<TDataSetRecInfo>= cannot access memory at adress 0x58

It tried without success:

Code: Pascal  [Select][+][-]

1. {$MODE DELPHI } // <--- it is compiled with Delphi-Mode
2.      if PDataSetRecInfo(aBuffer + dsRecInfoOfs)<>nil then //don't helps, it passes every time
3.         with PDataSetRecInfo(aBuffer + dsRecInfoOfs)^ do begin
4.           riBookmarkFlag := bfCurrent;                       //sometimes error here
5.           riRecNo := 0;
6.         end;
7.  

Does anyone know how can I catch this Error or check to nil?

[ASerge]

...or check to nil?

Code: Pascal  [Select][+][-]

1. if aBuffer <> nil then

[SunyD]

Thanks, so easy I didn't see it 

[Ñuño_Martínez]

Just to clarify:

Code: Pascal  [Select][+][-]

1.      if PDataSetRecInfo(aBuffer + dsRecInfoOfs)<>nil then //don't helps, it passes every time

This doesn't help because NIL is a pointer to address x00000000, so NIL + anything <> NIL is TRUE in all cases.

[Kays]

Code: Pascal  [Select][+][-]

1. if aBuffer <> nil then

I like my code more descriptive:

Code: Pascal  [Select][+][-]

1. if assigned(aBuffer) then

http://www.freepascal.org/docs-html/rtl/system/assigned.html