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getwindowsdirectory    (netdll.dll???)

Posted on 1998-08-12
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Last Modified: 2010-04-04
Hi

  I use the function GetWindowsDirectory, I have no problem in win95 but in winnt 4, when the function is
  executed, its give me an error :
 
  var directory : string;
  GetWindowsDirectory(PChar(directory),Max_Path);

"""An exception as occurs (EAccessViolation) with the message access violation of address '77F66DEF'
of module 'netdll.dll'. Write of address '00403DD5'.Processus stop """

P.S.:(i translate from the french error)

I dont understand what going on.

Thanks                                          
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Question by:sierra20
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6 Comments
 
LVL 1

Expert Comment

by:rene_moeller
ID: 1361956
Hi sierra20,

I get the same error in NT, but this piece of code works:

var
  Buffer : PChar;
  BufferSize : integer;
begin
  BufferSize := 255;
  GetMem(Buffer, BufferSize);
  GetWindowsDirectory(Buffer, BufferSize);
  ShowMessage(StrPas(Buffer));
  FreeMem(Buffer);
end;

Rene_Moeller
0
 

Expert Comment

by:khenr29j
ID: 1361957
You need to allocate memory for the string before you let Windows overwrite it.  NT is probably more sensitive to memory overwrites and doesn't let you shoot yourself in the foot like Windows '95 does.

Corrected code:
var directory : string;
Begin
  SetLength(Directory, GetWindowsDirectory(Nil, 0)+1);
  GetWindowsDirectory(PChar(directory),Max_Path);
  // etc

The first line allocates enough memory to hold the length of the windows directory returned by GetWindowsDirectory(Nil, 0) and adds one character to hold the trailing null character.
Best wishes,
     -Kristoffer
0
 
LVL 4

Expert Comment

by:erajoj
ID: 1361958
Hi,
In Windows 95, everything seems to be allowed!? ;-)
You have to allocate heap space by setting the string length to MAX_PATH:

  var directory : string; // creates empty string

  SetLength( directory, MAX_PATH ); // allocates heap space
  GetWindowsDirectory(PChar(directory),MAX_PATH); // now working!

/// John

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LVL 4

Expert Comment

by:erajoj
ID: 1361959
Sorry!
I was too slow...

/// John
0
 

Author Comment

by:sierra20
ID: 1361960
Hi

Kristoffer, you can answers the question because you give me the best answers.

Thanks.

Sierra
0
 

Accepted Solution

by:
khenr29j earned 150 total points
ID: 1361961
Here you go Sierra.
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