下面的代码最少地演示了该问题。在后台线程中,我创建了一个有效的句柄数组并将其传递给WaitForMultipleObjects
,这成功地等待了对象。
但是,将完全相同的数组传递给MsgWaitForMultipleObjects
时,使用WAIT_FAILED
的函数调用失败(ERROR_INVALID_HANDLE
)。
我究竟做错了什么?
program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils, Windows, SyncObjs, Classes;
type
TMyThread = class(TThread)
protected
procedure Execute; override;
end;
procedure TMyThread.Execute;
var
LEvent : TEvent;
LWaitHandles : TWOHandleArray;
LPWaitHandles : PWOHandleArray;
LWaitResult : Cardinal;
begin
LEvent := TEvent.Create;
LWaitHandles[0] := LEvent.Handle;
LPWaitHandles := @LWaitHandles;
while not Terminated do begin
{Works -> LWaitResult := WaitForMultipleObjects(1, LPWaitHandles, false, INFINITE);}
{Fails ->} LWaitResult := MsgWaitForMultipleObjects(1, LPWaitHandles, false, INFINITE, QS_ALLINPUT);
case LWaitResult of
WAIT_OBJECT_0: WriteLn('Event 1 Signaled');
{ etc... }
WAIT_FAILED : WriteLn(SysErrorMessage(GetLastError));
end;
end;
end;
var
lt : TMyThread;
begin
lt := TMyThread.Create(false);
ReadLn;
end.
最佳答案
尽管这两个调用的handles参数的WinAPI签名是相同的:
_In_ const HANDLE *pHandles,
但是,RTL以不同的方式包装这些功能。
WaitForMultipleObjects
使用指针类型:lpHandles: PWOHandleArray;
而
MsgWaitForMultipleObjects
使用无类型的var
参数:var pHandles;
因此,必须将句柄数组直接传递给
MsgWaitForMultipleObjects
。即:
LWaitResult := MsgWaitForMultipleObjects(1, LWaitHandles, false, INFINITE, QS_ALLINPUT);