• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 235
  • Last Modified:

api call gives access violation

Te goal is to retrieve the current user when the program starts; username is a global string; However, this code generates an eaccessviolation error. Any assistance would be greatly appriciated.

procedure TForm1.FormCreate(Sender: TObject);
var
user:pchar;
nsize:cardinal;
begin
windows.GetUserName(user,nsize);
username:=strpas(user);
end;
0
temporalnomad
Asked:
temporalnomad
1 Solution
 
shaneholmesCommented:

I dont get an access violation with your code :

procedure TForm1.FormCreate(Sender: TObject);
var
 user:pchar;
 nsize:cardinal;
 UserName: String;
begin
 GetUserName(user,nsize);
 UserName:= strpas(user);
end;

Shane
0
 
shaneholmesCommented:
Although, it doesn't work either

try

var
 i : cardinal;
 user:string;
begin
 i:= 255;
 setlength(user,i);
 getusername(pchar(user),i);
 setlength(user,(i-1));
 showmessage(user);
end;

SHane
0
 
robert_marquardtCommented:
function Username: string;
var
  Buffer: array [0..255] of Char;
begin
  Windows.getusername(@Buffer[0], SizeOf(Buffer));
  Result := Buffer;
end;

This should work (untested).
The original code is completely wrong because it does not allocate a buffer at all.
user is an uninitialized local pointer variable so getusername tries to overwrite a random memory area.
nsize is also uninitialized.
0
Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
tobjectpascalCommented:
procedure TForm1.Button1Click(Sender: TObject);
var
 UserN: String;
 Len: Dword;
begin
 SetLength(UserN,255);
 Len:=Length(UserN);
 GetUserName(@UserN[1],Len);
 ShowMessage(Trim(UserN)); // UserN:=Trim(UserN);
end;


Code works and tested under 2K, i find it very strange that it refuses to allow GetUserName(whatever,255); very strict.
0
 
tobjectpascalCommented:
Oh yeah now i see why, it has to modify the dword param :)

procedure TForm1.Button1Click(Sender: TObject);
var
 UserN: String;
 Len: Dword;
begin
 SetLength(UserN,255);
 Len:=Length(UserN);
 GetUserName(@UserN[1],Len);
 SetLength(UserN,Len-1);
 ShowMessage(UserN);
end;
0
 
shaneholmesCommented:
I can't believe you gave robert_marquardt the points.

Not only did i provide a perfectly good working answer, but i was the first to provide it.

 robert_marquardt,  took my answer and ran with it, changing it to use a buffer array instead.


Shane
0
 
tobjectpascalCommented:
var
  Buffer: array [0..255] of Char;
begin
  Windows.getusername(@Buffer[0], SizeOf(Buffer));
  Result := Buffer;
End;


Does not compile under Delphi 5 AT ALL so yeah as to why he would accept that is beyond me.
0
 
temporalnomadAuthor Commented:
he gave me the info i was really looking for, about the uninitialized pointer...but i cannot figure out how to grant any 'assist' points...i am new to EE. And i will give you each some, because all responses _were_ helpful...but as i said, i do not know how.
0
 
shaneholmesCommented:
Dont worry about it.

Thanks for acknowledging though!

Good luck!

Shane
0

Featured Post

Hire Technology Freelancers with Gigs

Work with freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely, and get projects done right.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now