Delphi调用DLL时出现的问题.
VC++写的DLL中代码为:
extern "C " __declspec( dllexport ) void SetParameter( double dVel, double dOffVel, double dLaserOn, double dPoly,
double dLaserOff, double dPos, double dDis, long lFreq, double dPower )
{
AFX_MANAGE_STATE(AfxGetStaticModuleState());
CLsrEllipseApp *pApp = ( CLsrEllipseApp* )AfxGetApp();
pApp-> SetParameter( dVel, dOffVel, dLaserOn, dPoly, dLaserOff, dPos, dDis, lFreq, dPower );
}
extern "C " __declspec( dllexport ) void MarkEllipse( double dX, double dY, double dWid, double dHei, double dRotAng )
{
AFX_MANAGE_STATE(AfxGetStaticModuleState());
CLsrEllipseApp *pApp = ( CLsrEllipseApp* )AfxGetApp();
pApp-> MarkEllipse( dX, dY, dWid, dHei, dRotAng );
}
我在Delphi中这样调用的:
procedure TMainInterface.Button1Click(Sender: TObject);
var
Init:function: Longint ;stdcall;
SetParameter:procedure (dVel:double;dOffVel:double;dLaserOn:double;dPoly:double;
dLaserOff:double;dPos:double;dDis:double;lFreq:longint;dPower:double);stdcall;
MarkEllipse:procedure (dX:double;dY:double;dWid:double;dHei:double;dRot:double);stdcall;
DllModule:THandle;

begin

DllModule:=LoadLibrary( 'LsrEllipse.dll '); // "LsrEllipse.dll "氦濂蟋M秸ノ害a}哦
if DllModule <> 0 then

@Init:=GetProcAddress(DllModule, 'Init '); //DLLいㄧ计Init()害a}
@SetParameter:=GetProcAddress(DllModule, 'SetParameter '); //DLLいㄧ计SetParameter()害a}
@MarkEllipse:=GetProcAddress(DllModule, 'MarkEllipse '); //DLLいㄧ计MarkEllipse()害a}

if (@Init <> nil)then
if (@SetParameter <> nil)then
if (@MarkEllipse <> nil)then
begin
Init(); //秸ノㄧ计Init
SetParameter(100,2000,0.0002,0.2,0.6,1,0.2,1000,0.6); //秸ノㄧ计SetParameter
MarkEllipse(10,10,2,5,45); //秸ノㄧ计MarkEllipse
FreeLibrary(DllModule);
end;
end;

运行时出现了错误:
Project Project1.exe raised exception class EAccessViolation with message 'Access violation at address 00000000.Read of address 00000000 '



[解决办法]
VC的函数声明中不加__stdcall，采用VC默认格式__cdecl，需要在Delphi中要注明调用格式为cdecl。

var
Init:function: Longint; cdecl;
SetParameter:procedure (dVel:double;dOffVel:double;dLaserOn:double;dPoly:double;
dLaserOff:double;dPos:double;dDis:double;lFreq:longint;dPower:double); cdecl;
MarkEllipse:procedure (dX:double;dY:double;dWid:double;dHei:double;dRot:double); cdecl;