How do I properly use the WaitForSingleObject method to wait for an external program to terminate?

Question

I'm trying to launch an external application with elevated status, and wait until it exits before continuing:

var
  FProcess: THandle;
  ExecInfo: TShellExecuteInfo;
begin

  FillChar(ExecInfo, SizeOf(ExecInfo), 0);
  with ExecInfo do
  begin
    cbSize := SizeOf(ExecInfo);
    fMask := 0;
    Wnd := AWindow;
    lpVerb := 'runas';
    lpFile := PChar(APath);
    lpParameters := PChar(AParams);
    lpDirectory := PChar(AWorkDir);
    nShow := SW_NORMAL;
  end;

  Result := ShellExecuteEx(@ExecInfo);

  if Wait then
  begin
    while WaitForSingleObject(ExecInfo.hProcess, INFINITE) <> WAIT_TIMEOUT do
      Application.ProcessMessages;
  end;

This launches, but it just keeps waiting. The calling program never continues past the call to WaitForSingleObject, even after the called program exits.

I've tried WAIT_OBJECT_0 instead of WAIT_TIMEOUT, but I have the same problem. What am I doing wrong here?

Answer 1

What the code

while WaitForSingleObject(ExecInfo.hProcess, INFINITE) <> WAIT_TIMEOUT do
  Application.ProcessMessages;

is supposed to do? It is an infinite loop.

Use just

WaitForSingleObject(ExecInfo.hProcess, INFINITE);

instead. And yes, you need

fMask:= SEE_MASK_NOCLOSEPROCESS;

to obtain the process handle.