I have two classes first class contains the object of another class as static but C++ doesnot allow me to do this and gives me some error.
source.cpp
#include"control.h"
int main()
{
Controller cnt;
cnt.tempcont();
return 0;
}
control.h
#include"recorder.h"
class Controller
{
public:
static recorder rec;
void tempcont();
};
recorder Controller::rec;
control.cpp
#include"control.h"
void Controller::tempcont()
{
rec.temprec();
}
recorder.h
#include<iostream>
using namespace std;
class recorder
{
public:
int a;
void temprec();
};
recorder.cpp
#include"recorder.h"
void recorder::temprec()
{
cout << "temp rec called";
}
I am getting the following errors and i have no idea why these errors are comming..
Error LNK1169 one or more multiply defined symbols found
Error LNK2005 "public: static class recorder Controller::rec" (?rec#Controller##2Vrecorder##A) already defined in control.obj
You define the variable Controller::rec in the header file. That means the variable will be defined in every translation unit where that header file have been included. It should only be defined in one single translation unit.
This is very easy to do: Just move the definition to a single source file.
Related
I am getting error code C2512 which is no appropriate default constructor available. However it appears to me that everything should be working so I am a bit confused on how to get this to compile.
Here is the header file code:
namespace MyNamespace
{
ref class ForwadDeclaredClass;
public ref class MyClass
{
public:
MyClass();
// ...
private:
ForwadDeclaredClass^ fc;
}
}
Now in my cpp file I define the forwarded class and try to use it in the constructor for MyClass.
using namespace MyNamespace;
//...
public ref class ForwardDeclaredClass
{
public:
ForwardDeclaredClass()
{
}
}
MyClass::MyClass()
{
// Compiler complains with error code here
fc = gcnew ForwardDeclaredClass();
}
I know I have to be missing something simple but I am just not seeing it. Any help would be appreciated.
At first glance, it looks like your namespaces are off.
In the header file, you're declaring ForwardDeclaredClass and MyClass inside MyNamespace.
In the cpp file, you're using MyNamespace, but the code you're writing isn't inside the namespace.
It looks like you need to enclose most of the contents of the cpp file in a namespace MyNamespace { block.
I wish to call C++ function (here Score()) which is present in Score_Update1.dll.
Both C# & C++ files get compiled successfully. I have also put above dll into the Debug/bin of C# project. But when I run C# code it gives EntryPointNotFoundException.
What could be the reason behind this Exception?
I tried dependency walker for Score_Update1.dll. But it doesn't show any Entry Point
I wish to use PInvoke technique for calling C++ function from C#
// Score_Update1.h
#pragma once
#include <iostream>
using namespace std;
using namespace System;
extern "C"{
#define MYAPI __declspec(dllexport)
namespace Score_Update1 {
public class MYAPI UpdateScore
{
// TODO: Add your methods for this class here.
public:
void Score();
};
}
}
// This is the main Score_Updat1.dll DLL file.
#include "stdafx.h"
#include "Score_Update1.h"
using namespace Score_Update1;
void UpdateScore::Score()
{
cout<<"Score has been updated";
}
C# code is as follows:
using Score_Update1;
using System.Runtime.InteropServices;
namespace GameTesting
{
class Game
{
[DllImport("Score_Update1.dll")]
internal extern static void Score();
static void Main(string[] args)
{
try
{
Game.Score();
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
}
}
The reason for EntryPointNotFoundException is that the DLL does not contain an entry point named Score. If you look at the exported names using dumpbin or some similar tool you will see mangled names.
However, using the mangled name isn't going to help you here. You've exported a class and the function you want to call is a member function. You cannot directly instantiate a C++ class from pinvoke. And you cannot call member functions. If you wish to use pinvoke you would need to flatten the class to a C style interface. Another route would be to compile the C++ code to a mixed mode C++/CLI assembly and consume that.
I'm programming in Visual C++ 2010. I've got a example.h example.cpp and Form1.h.
Basically, I've pasted bits of code. I'm not able to include Form1.h in the example.h file, not sure why. But The main question is how do I call Test (which is in form1.h) from example.cpp? What would be the syntax? Is it possible to do this?
My Form1.h
#include "example.h"
public ref class Form1 : public System::Windows::Forms::Form
{
public: void Test(void)
{
// Does something
}
}
My example.cpp
#include "example.h"
#include "Form1.h"
Test(); // would like to call Test from here.
You have two problems here:
You must call functions from inside of another function. The code you currently have in your example.cpp file is invalid, because you are trying to call the Test() function at global scope.
Make it look like this instead:
int main()
{
Test();
return 0;
}
This also solves the problem that you don't have a main function, which is the entry point to any C++ application.
More generally, I would strongly recommend using one of the project templates that comes with Visual Studio to get started (rather than copying and pasting random bits of code, like you said). That ensures that you have all of the things you need to get started, like an entry point. Once you have a solid foundation, you can start building up from there.
You might also find it useful to obtain either a book on C++/CLI or an online tutorial (such as this one: Hello C++/CLI, Part 1 and Hello C++/CLI, Part 2).
Your Test function is a member function of the Form1 class, which means that you need an object of that class in order to call it. Thus, the code should actually look like this:
int main()
{
Form1^ frm = gcnew Form1();
frm.Test();
return 0;
}
Alternatively, you could work around this by making the Test() function a static function. This would allow you to call it without having an instance of the class:
public ref class Form1 : public System::Windows::Forms::Form
{
public: static void Test(void)
{
// Does something
}
}
// ...
int main()
{
Form1::Test();
return 0;
}
However, beware that this means you cannot access any other members of the Form1 class inside of the Test() function (because there is no this pointer).
This should all be explained in whatever book/tutorial you decide to use to learn C++/CLI—search for a chapter about "Classes" or "Object-Oriented Design".
Is it possible to use for case 1 one header and for case 2 another?
Because when I use both headers in program I've got ambiguous symbol errors.
header 1(winapifunctions.h)
#include <Windows.h>
void CallWindowProc(String^ windowtitle)
{
};
header 2(classes.h)
using namespace System;
using namespace System::Collections::Generic;
public delegate void Super();
public ref class Event{};
public ref class MyException:public DivideByZeroException{};
public interface class IType{};
public interface class IVal{};
public ref class Writer abstract{};
public ref class Check: public Writer,public IType,public IVal
.....other classes
main program
#include "stdafx.h"
#include "classes.h"
#include "winapifunctions.h"
int main(array<System::String^>^ args)
{
//read x
switch(x){ case 1: {CallWindowProc("title");break;} case 2: { Check^ obj = gcnew Check();break;}
};
and error - IServiceProvider:ambiguous symbol
Short answer: No.
Long answer: includes are processed by the pre-processor, during compile time, while your case statements are processed during runtime. There's no way to make a compile-time thing to happen during runtime.
What are you trying to achieve exactly?
You can work around this problem using the following code:
// 1.cpp
case 1:
DoCase1();
break;
case 2:
DoCase2();
break;
// 2.cpp
#include <Windows.h>
void DoCase1()
{
// ...
}
// 3.cpp
#include <AnotherHeader.h>
void DoCase2()
{
// ...
}
If you would post more code and exact error messages, perhaps a better solution can be found.
I am attempting to simply add a FilterInfo class to my FilterInfo collection. I'm having a terrible time trying to understand why the following code keeps throwing the error:
System::Collections::Generic::List::Add'
: cannot convert parameter 1 from
'Ziz::FilterInfo *' to
'Ziz::FilterInfo'
I'm only learning C++/CLI, as I'm a C# developer, and I'm sure it's something simple, but I sure could use some pointers. My stripped code is as follows:
public value class FilterInfo
{
public:
char* Address;
};
public ref class Ziz
{
private:
List<FilterInfo>^ _blockList;
public:
// Constructor
Ziz(){
_blockList = gcnew List<FilterInfo>();
}
List<FilterInfo>^ GetBlockList()
{
for each(_IPFILTERINFO ip in _packetFilter->GetBlockList())
{
// _IPFILTERINFO is the native C++ struct.
FilterInfo* f = new FilterInfo();
_blockList->Add(f);
}
return _blockList;
}
You declared _blockList as
List<FilterInfo>^ _blockList;
but you are trying to add
FilterInfo* f
to it. It cannot work since one is a pointer and the other one is a reference.
I'm not sure how "value" fits in but in
public value class FilterInfo
{
public:
char* Address;
};
You are derefore declaring an unmanaged class
to make it managed, you should use
public ref class FiterInfo
This will allow you to use FilterInfo* without having to manage memory explicitely.
Finally, char* is not so great in C++/CLI, I would recommend using System::String
_blockList->Add(*f);
You have to construct your FilterInfo with gcnew as well. You can't really mix and mash these together without marshaling.
FilterInfo is not FilterInfo*. If you want a List of pointers to FilterInfo, you need to say that List<FilterInfo*>. Since FilterInfo is a value class here though you'll likely just want to skip the new.
FilterInfo fi;
_blockList->Add(fi);
public ref class A
{
};
int main(array<System::String ^> ^args)
{
Console::WriteLine(L"Hello World");
ICollection<A^>^ oCollection = gcnew List<A^>();
oCollection->Add(gcnew A());
return 0;
}