How can I solve this?

Question

C++ h.file

//unsigned int NorthWall[256]; 
//unsigned int EastWall[256];  
unsigned int NorthWall[256]; 
unsigned int EastWall[256]; 
unsigned int NorthWall_Flash[256]; 
unsigned int EastWall_Flash[256];  

C++ cpp.file

void SearchToGoal(unsigned int* northWall, unsigned int* eastWall)
{
 DashFlag=0;
 Solver(CurrentXY, DashFlag);
 BestPathFinder(Goal_XY1, Goal_XY2, Goal_XY3, Goal_XY4, DashFlag);
 MCommandGen(Goal_XY1, Goal_XY2, Goal_XY3, Goal_XY4);
    NorthWall = northWall; //y
    EastWall = eastWall;  //x

}

***The errors are the bold worlds.. ERROR: expression must be a modifiable lvalue***

Answer 1

What are you trying to do? Are you trying to copy the contents of the array pointed to by northWall to the array defined by NorthWall? Or are you trying to assign a pointer to an array to another pointer?

Answer 2

I'm trying to pass an array from my C# program to this C++ program.. what else I have to show you in order for you to know how to help me?

Answer 3

If you want to copy the contents of the array, then use memcpy(), as in:

memcpy (NorthWall, northWall, sizeof (NorthWall));

You need to ensure that the array size of NorthWall is sufficient.

By the way, where is your C# code? Are you using PInvoke to call the C++ function?

Answer 4

my c# ARRAY.... still have some errors (those bold ones)

got wall means 1, no wall means 0

        //Wall array
        //Vertical (16x16)
        int[][] a = new int[][]   {new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},                            
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                   new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
        //Horizontal (16x16)
        int[][] b = new int[][]{ new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                 new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};

        int x = 0;
        int y = 0;

        //Mouse array
        //Vertical (16x16)
        int[][] northWall = new int[][]{new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},                            
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
        //Horizontal (16x16)
        int[][] eastWall = new int[][]{ new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
                                        new int[] { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};

        int x1 = 0;
        int y1 = 0;

.............

................

.......................

        private void btnRun_Click(object sender, EventArgs e)
        {
            timer1.Enabled = true;
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            label7.Text = Convert.ToString(Add(5.0, 6.0));

            northWall[15][0] = a[15][0]; // x=0,y=0
            eastWall[14][0] = b[14][0];
            // pass to solver
            // solver(...)
            SearchToGoal(northWall, eastWall);
            // solver return mouse command
            //mouse move .. update x ,y
            northWall[15 - y][0] = a[15 - y][0]; // x=0,y=1
            eastWall[14 - y][0] = b[14 - y][0];
            // pass to solver
            northWall[15 - y][x] = a[15 - y][x]; // x=1,y=1
            eastWall[14 - y][x] = b[14 - y][x];
        }

Answer 5

Hi Melsoon

Just in case nobody has mentioned it, the compilation error means that you are trying to assign value to an array pointer which is constant. As Brian Muth put it, you need to replace

     NorthWall = northWall;//compiler error because NorthWall is constant

with

    memcpy(NorthWall,northWall,sizeof(NorthWall));

Or, if some permanent memory space is created in the program for NorthWall, NorthWall should be declared as a pointer.

Best regards

Chong

Answer 6

You also overlooked the fact that a C# int is a 64 bit number, and you are trying to copy it to a 32-bit integer.

Use long long instead.

Answer 7

TIP: All of those explicit zero initializers are
unnecessary, You can use default-initialization.

int *ip = new int[16]; // uninitialized

int *ip = new int[16](); // default initialized

The default initialization for an int is zero,
so the last example sets all the ints in the
allocation to zero.

- Wayne

Answer 8

You also overlooked the fact that a C# int is a 64 bit number, and you are trying to copy it to a 32-bit integer.

Brian, I don't think so. See
 
http://msdn.microsoft.com/en-us/library/exx3b86w.aspx
 
It seems that long in C# is 64 bits (unlike in Visual C++), but int is 32 bits (same as in Visual C++).
 

---

David Wilkinson | Visual C++ MVP

Answer 9

Hi all, thank you for ur help!

how about the error for this....

SearchToGoal(northWall, eastWall);

*error: The best overload method match for 'CreateMaze.Form1.SearchToGoal(ref int[], ref int[])' has some invalid arguments

I imported the dll file over to my C#...

       [DllImport("solver.dll")]
       public static extern void SearchToGoal(ref int[] a1, ref int[] b1);

How am i suppose to even correct or write this?

            northWall[15][0] = a[15][0]; // x=0,y=0
            eastWall[14][0] = b[14][0];
            // pass to solver
            // solver(...)
            SearchToGoal(northWall, eastWall);
            // solver return mouse command
            //mouse move .. update x ,y
            northWall[15 - y][0] = a[15 - y][0]; // x=0,y=1
            eastWall[14 - y][0] = b[14 - y][0];
            // pass to solver
            northWall[15 - y][x] = a[15 - y][x]; // x=1,y=1
            eastWall[14 - y][x] = b[14 - y][x];

Please help! THANKS!

Answer 10

Brian, I don't think so. See
 
http://msdn.microsoft.com/en-us/library/exx3b86w.aspx
 

You're correct, David. My goof.

Answer 11

Hi Melsoom,

I found you have posted sevaral threads which have the similar topic these days in Visual C++ and Visual C# fourms. Didn't you solve this issue?

please refer to your former threads for information. what's more, do not post the same questions more than once.

Passing of arrays: http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/d182abf2-b8c6-4de2-8e84-453f24005fa6.

How to pass this array to my solver in C++: http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/08273b32-9b2d-49e6-bf1b-0583afcc55b9.

finally, please mark the reply which helps you as answer,.

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Please mark this reply as answer if it helps you! Thanks for your cooperation! Good Luck to you.

Answer 12

hi, there are still some errors that have not been solved.

Regards,
Melsoon

Answer 13

If the error is on VC# side, you should move to Visual C# forum for better support.

 NorthWall = northWall; //y
    EastWall = eastWall;  //x

}

***The errors are the bold worlds.. ERROR: expression must be a modifiable lvalue***

has this error been solved?

We are not allowed to assign C# value to C++ variable directly.

you can try C++/CLI wrapper.

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Please mark this reply as answer if it helps you! Thanks for your cooperation! Good Luck to you.

Answer 14

Hi Melsoon,

I agree with Rebecca. You can try C++/CLI wrapper in this situation. That is, we should create a C++/CLI wrapper for the C# class library(C# DLL), and invokes it through the warpper from the native C++ codes. If you want to know more information about this solution, please refer to this link which contains a sample routime: http://social.msdn.microsoft.com/Forums/en-US/vcgeneral/thread/0a0342e4-caec-42d0-bfe5-e0930883f141. What's more, you can also try the ways of Solution 2 and 3.

I hope this reply is helpful to you. If you have any questions, please feel free to let me know.
Best regards,

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Helen Zhao [MSFT]
MSDN Community Support | Feedback to us

Answer 15

hi, there are still some errors that have not been solved.
 
Regards,
Melsoon

The C++/CLI type corresponding to a two dimensional C# array of integers is
 
array<int, 2>
 
So in your C++/CLI module I think you should do
 
typedef array<int, 2> Matrix;
 
void SearchToGoal(Matrix^ northWall, Matrix^ eastWall)
{
  // fill elements of northWall, eastWall
}
 

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David Wilkinson | Visual C++ MVP