CreateProcess .. WaitForSingleObject .. CloseHandle 调用的最佳 try..finally 放置

Question

我想在调用 CreateProcess..WaitForSingleObject 后调用 CloseHandle，并希望将 CloseHandle 调用包含在 try..finally 块中，但不确定将不同的调用放在哪里 w.r.t。尝试..终于.

这是我当前的代码：

var
  p, f, a: String;
  pi: TProcessInformation;
  si: TStartupInfo;
begin
  Log('Starting backup..');

  if (not FileExists(FMYPROG)) then
  begin
    Log('Error: ' + STR_ERRMSG_1);
    MessageDlg(STR_ERRMSG_1, mtError, [mbOK], 0);
    Exit;
  end;

  // start process up
  FillChar(si, SizeOf(si), 0);
  si.cb := SizeOf(si);
  si.dwFlags := STARTF_USESHOWWINDOW;
  si.wShowWindow := SW_NORMAL;

  f := IncludeTrailingPathDelimiter(FBAKFILEPATH) + 'output.bak';
  p := '/changesonly "' + f + '"';

  try   // is this the optimal placement for this line? or should it be after CreateProcess? 
    if CreateProcess(PChar(FMYPROG), PChar(p), nil, nil, False,
      CREATE_NEW_PROCESS_GROUP + NORMAL_PRIORITY_CLASS, nil, PChar(ExtractFilePath(FMYPROG)), si, pi) then
      WaitForSingleObject(pi.hProcess, INFINITE)
    else
      RaiseLastOSError;

  finally
    CloseHandle(pi.hProcess);
    CloseHandle(pi.hThread);
  end;

导致 Delphi 寻求启发的建议和批评。谢谢。

Answer 1

仅在 CreateProcess 成功时才调用 CloseHandle。因此它是这样的：

if CreateProcess(...) then
  try
    ....
  finally
    // calls to CloseHandle
  end
else
  RaiseLastOSError;

或者如果您更愿意预先处理错误情况：

if not CreateProcess(...) then
  RaiseLastOSError;
try
  ....
finally
  // calls to CloseHandle
end

这在语义上是相同的，因为您知道 RaiseLastOSError 会引发异常。

或者如我所愿：

Win32Check(CreateProcess(...));
try 
  ....
finally
  // calls to CloseHandle
end;

Win32Check便利函数简单封装了逻辑

if not Succeeded then
  RaiseLastOSError;

CreateProcess .. WaitForSingleObject .. CloseHandle 调用的最佳 try..finally 放置

Optimal try..finally placement for CreateProcess .. WaitForSingleObject .. CloseHandle calls

delphi

createprocess