c# 调用C++ 结构体指针的问题： 尝试读取或写入受保护的内存。这通常指示其他内存已损坏
typedef struct _vehicles_info
{
int idx;
/*
* 车牌号码
*/
char vehicle_name[32];
/*
* rtsp信息
*/
char vehicle_rtsp[256];
//0 offline, 1 online
Byte status;
}VehicleInfo;
方法：int GetVehiclesInfo(VehicleInfo *pVehicle, int size);
转为C#方法后的代码如下：
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public unsafe struct VehicleInfo
{
public int idx;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string vehicle_name;//车牌号码
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string vehicle_rtsp;//rtsp信息
public byte bstatus;//0 offline, 1 online
};
方法：
[DllImport("UserClient.dll", CallingConvention = CallingConvention.Cdecl)]
public unsafe static extern int GetVehiclesInfo(IntPtr[] p, int size);
调用代码如下：
IntPtr[] record = new IntPtr[isize]; //申请内存空间
record[0] = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(BwsPtzManager.VehicleInfo)) * isize);
int realcount = BwsPtzManager.GetVehiclesInfo(record, isize);
for (int i = 0; i < realcount; i++)
{
BwsPtzManager.VehicleInfo vehinfo = new BwsPtzManager.VehicleInfo();
vehinfo = (BwsPtzManager.VehicleInfo)Marshal.PtrToStructure((IntPtr)((UInt32)record[i]), typeof(BwsPtzManager.VehicleInfo));
Marshal.FreeHGlobal(record[i]);
}
问题来了：代码运行到 vehinfo = (BwsPtzManager.VehicleInfo)Marshal.PtrToStructure((IntPtr)((UInt32)record[i]), typeof(BwsPtzManager.VehicleInfo)); 这里的时候，总是报 “尝试读取或写入受保护的内存。这通常指示其他内存已损坏”的错误，求大神指点。已经折腾的快挂了。总找不到原因。
另附c++代码如下：
VehicleInfo *pVehicle = (VehicleInfo*)malloc(sizeof(VehicleInfo)*count) ;
memset(pVehicle, 0x00, sizeof(VehicleInfo)*count);
int realcount = GetVehiclesInfo(pVehicle, count);
printf("%d\n", realcount);
for(int i = 0; i < realcount; i++)
{
printf("%s,%s,%d\n", pVehicle[i].vehicle_name,pVehicle[i].vehicle_rtsp,pVehicle[i].status );
}
运行一切正常，没任何问题。神救救我吧 展开
我用你的代码验证了一下我的猜测。
有两处错误
1 c++的dll 方法：int GetVehiclesInfo(VehicleInfo *pVehicle, int size);
参数是指针数组 应该使用 VehicleInfo **pVehicle
所以应该为int GetVehiclesInfo(VehicleInfo **pVehicle, int size);
DLL中的方法 为了测试加了一个MessageBoxA
VEC_API int GetVehiclesInfo(VehicleInfo **pVehicle, int size)
{
for(int i =0;i<size;i++)
{
pVehicle[i]->vehicle_name[0]='H';
pVehicle[i]->vehicle_name[1]='A';
pVehicle[i]->vehicle_name[2]='U';
pVehicle[i]->vehicle_name[3]='0';
pVehicle[i]->vehicle_name[4]='9';
pVehicle[i]->vehicle_name[5]='8';
pVehicle[i]->idx=1;
pVehicle[i]->vehicle_rtsp[0]='1';
pVehicle[i]->vehicle_rtsp[1]='2';
}
string s(pVehicle[0]->vehicle_rtsp);
MessageBoxA(NULL,pVehicle[0]->vehicle_name,"pVehicle[0]的车牌号码是",0);
return 0;
}
2 c#
record[0] = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(BwsPtzManager.VehicleInfo)) * isize);
像这样分配地址是不对的 ，这样只是给record[0] 分配了 record[size] 长度地址空间
而并没有给 record[1]~ record[size-1]分配空间
所以应该为
IntPtr[] record = new IntPtr[isize]; //申请内存空间
for (int i = 0; i < isize; i++)
{
record[i] = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(VehicleInfo)));
}
按钮事件:
private void button1_Click(object sender, EventArgs e)
{
int isize=5;
IntPtr[] record = new IntPtr[isize]; //申请内存空间
for (int i = 0; i < isize; i++)
{
record[i] = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(VehicleInfo)));
}
int realcount = GetVehiclesInfo(record, isize);
for (int i = 0; i < realcount; i++)
{
VehicleInfo vehinfo = new VehicleInfo();
vehinfo = (VehicleInfo)Marshal.PtrToStructure((IntPtr)((UInt32)record[i]), typeof(VehicleInfo));
Marshal.FreeHGlobal(record[i]);
}
}
[DllImport("vec.dll", CallingConvention = CallingConvention.Cdecl)]
public unsafe static extern int GetVehiclesInfo( IntPtr[] p, int size);
首先很感谢您的回答,很详细.我还有个疑问
int GetVehiclesInfo(VehicleInfo *pVehicle, int size);
这个接口既然有问题的话,C++代码调用为何没有问题呢?因为这个接口不是我写的,所以要让别人改接口,必须证明他这个写法确实是错的.
因为C#传的是指针数组 ，而C++的调用是传的指针分配空间的首地址。所以不是他这样写不正确，是想让C++和C#都能用，就只能用指针数组。
