如何在Delphi中的多个线程中加载DLL？

Question

也许有一些我错过的东西,我无法想象这里发生了什么.

我正在尝试在TThread对象的多个实例中加载相同的DLL.

这是我的DLL代码:

library MyCalcFor32;

uses
  SysUtils,
  Classes,
  uRunner in 'uRunner.pas';

Exports EVal;

{$R *.res}

begin
end.

这是uRunner.pas:

unit uRunner;

interface

uses SysUtils,
     Classes;

function EVal(Valor: WideString): WideString; stdcall; export;

implementation

function EVal(Value: WideString): WideString; stdcall; export;
begin
  Result := Value+' xxx';
end;

initialization

finalization

end.

这是加载DLL的程序:

procedure TfrmMain.FormCreate(Sender: TObject);
var I: Integer;
begin
  SetLength(Threads, 10);
  for I:= 0 to 9 do
  begin
    Threads[I] := TWorker.Create(Self.Handle, I+1, Memo1.Text, ExtractFilePath(ParamStr(0)));
  end;
end;


procedure TfrmMain.btnExecuteThreadsClick(Sender: TObject);
var I: Integer;
begin
  ClearMemos([MT1, MT2, MT3, MT4, MT5, MT6, MT7, MT8, MT9, MT10]);

  for I:= 0 to 0 do //to 9, for multiple
  begin
    if Threads[I].Suspended then
      Threads[I].Resume
    else
      ShowMessage('Thread already in execution');
  end;
end;

procedure TWorker.Execute;
var I: Integer;
    J: Cardinal;

    Ret: WideString;

    A,B,C: Extended;       
begin
  CoInitialize(nil);
  try
    LoadDll;

    while not Terminated do
    begin
      if not (Suspended or Terminated) then
      begin
        A := 310132041025;
        B := 17592186044416;
        C := 0;

        for I:= 0 to 10 do
        begin

          if (Terminated) then begin
            Break;
          end;

          for J:= 0 to 9999999 do
          begin

            if (Terminated) then begin
              Break;
            end;

            A:= Sqrt(A);

            if A <= 0 then begin
              A:= 310132041025;
            end
            else begin
              A:= Math.Power(A, 2);
            end;

            C:= C + (B-34 / 4);

            B:= B / 2;

            if B <= 0 then begin
              B:= 17592186044416;
            end;
          end;

          Ret := FEvalProcAddress(FEValValue);

          NotifyMainForm(Format('Evaluate %s, resulted in %s', [IntToStr(I), Ret]));
        end;
        Suspend;
      end;

      Sleep(5000);
    end;
  finally
    CoUninitialize;
  end;
end;  

procedure TWorker.LoadDll;
begin
  //GlobalLock.Enter;
  //try
    FDLLHandle := LoadLibraryA(PChar(FPathApp + 'MyCalcFor32.dll'));
  //finally
  //  GlobalLock.Leave;
  //end;

  if GetLastError <> 0 then
  begin
    NotifyTerminateThread;
  end
  else
  begin
    FEvalProcAddress := GetProcAddress(FDLLHandle, PChar('EVal'));

    if GetLastError <> 0 then
    begin
      NotifyTerminateThread;
    end;
  end;
end;

当我只有一个线程时,它工作得很好,但是当我使用多个线程时它会引发以下异常:

System Error.  Code: 87.
Incorrect Parameter

注意:上面的代码仅用于复制;
我知道WideString + AnsiString问题.

Answer 1

您正在错误地执行错误检查.GetLastError如果函数失败,您只需要调用.我希望您GetLastError在API调用成功后调用,而不是所有API调用SetLastError(0)在返回成功时调用.因此,您正在选择一个不适用于您所进行的函数调用的陈旧错误代码.

要检查失败,对于这些函数,您需要检查返回值.

• LoadLibrary通过返回报告失败0.
• GetProcAddress通过返回报告失败nil.

您必须仔细阅读这些函数的文档,但这是一个非常常见的主题.每个Win32 API函数都可能以不同方式处理错误.分别阅读每个功能的文档.