c++实现虚类定义在dll外，在dll内

c++ implement virtual class defined outside dll,in dll

本文关键字：dll 定义 实现 c++      更新时间：2023-10-16

如何在Windows VS2010中做到这一点?

相同解决方案下的2个项目:第一个是常规控制台应用程序，包含两个文件:s.h和j.p p。第二个项目是一个带有一个头文件的dll应用程序:j.h

s.h: 

#ifndef M
#define M
class MyMathFuncs
    {
    public: 
        // Returns a + b
        virtual double Add(double a, double b) const = 0; 
        // Returns a - b
        virtual double Subtract(double a, double b) const = 0; 
        // Returns a * b
        virtual double Multiply(double a, double b) const = 0; 
        // Returns a / b
        // Throws const std::invalid_argument& if b is 0
        virtual double Divide(double a, double b) const = 0; 
    };
double MyMathFuncs::Add(double a, double b) const{}; 
        // Returns a - b
 double MyMathFuncs::Subtract(double a, double b) const{}; 
        // Returns a * b
 double MyMathFuncs::Multiply(double a, double b) const{}; 
        // Returns a / b
        // Throws const std::invalid_argument& if b is 0
 double MyMathFuncs::Divide(double a, double b) const{};

j.cpp: 

#include "s.h"
#include "j.h"
#include <iostream>
using namespace std;
int main()
{
    double a = 7.4;
    int b = 99;
    MyMathFuncs2 k;
    cout << "a + b = " <<
        k.Add(a, b) << endl;
    cout << "a - b = " <<
        k.Subtract(a, b) << endl;
    cout << "a * b = " <<
        k.Multiply(a, b) << endl;
    cout << "a / b = " <<
        k.Divide(a, b) << endl;
    try
    {
        cout << "a / 0 = " <<
            k.Divide(a, 0) << endl; 
    }
    catch (const invalid_argument &e) 
    {
        cout << "Caught exception: " << e.what() << endl; 
    }
    char c;
    cin >> c;
    return 0;
}

in dll, j.h:

#ifndef dllheader
#define dllheader
#include "s.h"
#include <stdexcept>
class MyMathFuncs2: public MyMathFuncs {
public:
     __declspec(dllexport) double Add(double a, double b) const  {
        return a + b;
    }
        // Returns a - b
     __declspec(dllexport) double Subtract(double a, double b) const {
        return a - b;
    }
        // Returns a * b
     __declspec(dllexport) double Multiply(double a, double b) const {
        return a * b * b * b;
    } 
        // Returns a / b
        // Throws const std::invalid_argument& if b is 0
     __declspec(dllexport) double Divide(double a, double b) const {
        if (b == 0)
        {
            //throw invalid_argument("b cannot be zero!");
        }
        return a / b;
    }
}

#endif

dll编译，但控制台应用程序不编译:

files (x86)microsoft visual studio 10.0vcincludetypeinfo(36): error C2236: unexpected 'struct' '__type_info_node'. Did you forget a ';'?
1>c:program files (x86)microsoft visual studio 10.0vcincludetypeinfo(36): error C2143: syntax error : missing ';' before '{'
1>c:program files (x86)microsoft visual studio 10.0vcincludetypeinfo(36): error C2447: '{' : missing function header (old-style formal list?)
1>c:program files (x86)microsoft visual studio 10.0vcincludetypeinfo(41): error C2146: syntax error : missing ';' before identifier '__type_info_root_node'
1>c:program files (x86)microsoft visual studio 10.0vcincludetypeinfo(41): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:program files (x86)microsoft visual studio 10.0vcincludetypeinfo(41): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:program files (x86)microsoft visual studio 10.0vcincludetypeinfo(67): error C2061: syntax error : identifier '__type_info_node'
1>c:program files (x86)microsoft visual studio 10.0vcincludetypeinfo(74): error C2061: syntax error : ide

在j.h中class MyMathFuncs2定义的末尾，请参见:

}

试试改成:

};
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