Why does SHParseDisplayName give an access violation if I've imported it myself?

Question

I get an access violation when trying to get a pidl form a path in Delphi, and the returned pidl is nil. This is my code:

type
  // TParseDisplayName = function(pszPath: PChar; pbc: pointer; var pidl: PItemIDList; sfgaoIn: LongWord; var psfgaoOut: LongWord): LongInt;
  TParseDisplayName = function(pszPath: PWideChar; pbc: IBindCtx; var pidl: PItemIDList; sfgaoIn: ULong; var psfgaoOut: ULong): HResult;

var
  SHParseDisplayName: TParseDisplayName;
  SHELL32DLLHandle : THandle;

procedure test();
var
  ws : WideString;
  tmpLongWord: ULong;
  lpItemID: PItemIDList;
begin
  //ws := 'Mes documents';

  CoInitialize(nil);

  // path to test
  ws := 'C:\inetsdk\Nouveau Document WordPad.doc';

  if (SHParseDisplayName(PWideChar(ws), nil, lpItemID, 0, tmpLongWord) = S_OK) then
    if not assigned(lpItemID) then      
      s := SysErrorMessage(getLastError);

  CoUnInitialize();
end;

initialization
  SHELL32DLLHandle  := LoadLibraryW('shell32.dll');

  @SHParseDisplayName := GetProcAddress(SHELL32DLLHandle, 'SHParseDisplayName');

score 6 · Accepted Answer · answered Oct 11 '11 at 08:51

6

The declaration of TParseDisplayName omits the calling convention. You need to include stdcall.

TParseDisplayName = function(pszPath: PWideChar; pbc: IBindCtx; 
  var pidl: PItemIDList; sfgaoIn: ULong; var psfgaoOut: ULong): HResult; stdcall;

When you don't specify a calling convention the default calling convention is used. The default calling convention is register. This has different semantics for parameter passing and clean up which leads to the type of runtime error you have experienced. Practically all Windows API functions used stdcall.

answered Oct 11 '11 at 08:51

David Heffernan

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Thanks a lot ! I really appreciate your quick help David ! – user382591 Oct 11 '11 at 08:56
1

My stalking downvoter is back. The funny thing is that this stalker only succeeds in reducing their own reputation. – David Heffernan Oct 11 '11 at 09:28
@Ken Actually blitzers do get the rep back. But no blitz attack from current stalker who knows how things work here. – David Heffernan Oct 11 '11 at 11:40
@David: That's why downvoting costs rep. And unless a whole bunch of people downvote, it's meaningless. I find that a lot of really good answers get both + and - votes. – Warren P Oct 11 '11 at 17:06

Why does SHParseDisplayName give an access violation if I've imported it myself?

1 Answers1