Creating C/C++ Dynamic Link Library (C/C++ DLL) Using Visual Studio

I was working on a project to create a C dynamic link library (.DLL). It seems difficult at the beginning. However, after several attempts, manage to produce it.

For creation of C++ library you can refer to the MSDN. I'm following these steps and enhance on the same codes to produce C DLL.

1. In order to access a library file, we can utilize the Dependency Walker.
2. The library that generated by the sample code by MSDN is as picture below. Take note of the difference between C++ functions and C functions.
   
3. To export C functions, we can the export function names in .def file
   
4. Header file will look something like this. The function for the Add is normal declaration in Header file.
   
   
5. The implementation code is a standard code.
1. #include "stdafx.h"
2. 
   
3. #include "CryptoCPPDLL.h"
4. #include <stdexcept>
5. 
   
6. using namespace std;
7. 
   
8. namespace CryptoFuncs
9. {
10.     double CryptoCPPDLL::Add(double a, double b)
11.     {
12.         return a + b;
13.     }
14. 
    
15.     double CryptoCPPDLL::Subtract(double a, double b)
16.     {
17.         return a - b;
18.     }
19. 
    
20.     double CryptoCPPDLL::Multiply(double a, double b)
21.     {
22.         return a * b;
23.     }
24. 
    
25.     double CryptoCPPDLL::Divide(double a, double b)
26.     {
27.         if (b == 0)
28.         {
29.             throw invalid_argument("b cannot be zero!");
30.         }
31. 
    
32.         return a / b;
33.     }
34. 
    
35. double CryptoCPPDLL::Add2(double a, double b)
36.     {
37.         return a + b;
38.     }
39. 
    
40.     double CryptoCPPDLL::Subtract2(double a, double b)
41.     {
42.         return a - b;
43.     }
44. 
    
45.     double CryptoCPPDLL::Multiply2(double a, double b)
46.     {
47.         return a * b;
48.     }
49. 
    
50.     double CryptoCPPDLL::Divide2(double a, double b)
51.     {
52.         if (b == 0)
53.         {
54.             throw invalid_argument("b cannot be zero!");
55.         }
56. 
    
57.         return a / b;
58.     }
60. void CryptoCPPDLL::PassStructIn(MyStruct* myStruct)
61. {
62.       if (myStruct != NULL)
63.       {
64. 
    
65.             myStruct->SomeId = 234;
66.             myStruct->SomePrice = 456.23;
67.       }
68. }
70. void CryptoCPPDLL::PassStructIn2(MyStruct* myStruct)
71. {
72.       if (myStruct != NULL)
73.       {
74. 
    
75.             myStruct->SomeId = 234;
76.             myStruct->SomePrice = 456.23;
77.       }
78. }
79. 
    
80. void PassStructIn3(MyStruct* myStruct)
81. {
82.       if (myStruct != NULL)
83.       {
84. 
    
85.             myStruct->SomeId = 234;
86.             myStruct->SomePrice = 456.23;
87.       }
88. }
89. 
    
90. double Add3(double a, double b)
91. {
92. return a + b;
93. }
94. 
    
95. }
6. The second way to do this is through extern "C" __declspec(dllexport) YOUR_FUNCTION_NAME.
7. Hope this helps. I will create another post to how to do it in Eclipse using GCC.