Introduction to C ++ conventional DLL Application

The DLL application in C ++ is a very important basic concept in actual programming. mastering this application plays an important role in program development. Here we will give a detailed introduction to C ++ conventional DLL, hoping to help you.

C ++ conventional DLL creation and use

1: export functions

 
 

  
  
__declspec(dllexport) void ShowDlg(void)  
  
  
{  
  
  
CDllDialog dllDialog;  
  
  
dllDialog.DoModal ();  
  
  
} 
 
 

2: Modify the. def file and add the function name.

 
 

  
  
; DrawTestDll.def : Declares the module parameters for the DLL.  
  
  
 
  
  
LIBRARY "DrawTestDll"  
  
  
DESCRIPTION 'DrawTestDll Windows Dynamic Link Library'  
  
  
 
  
  
EXPORTS  
  
  
; Explicit exports can go here 
 
 

3: copy the DLL file to the directory where the program is located.

4: Call the DLL in the program

 
 

  
  
Void CDllTestView: OnLButtonDown (UINT nFlags, CPoint point)
  
  
{
  
  
Typedef void (* lpFun) (void );
  
  
HINSTANCE hDll; // DLL handle
  
  
HDll = LoadLibrary ("DrawTestDll. dll"); // load DLL Resources
  
  
If (NULL = hDll) // search for the sequence, directory where EXE is located, directory where the project is located, and directory of System and windows
  
  
{
  
  
MessageBox ("DLL loading failed ");
  
  
}
  
  
LpFun addFun; // function pointer
  
  
AddFun = (lpFun) GetProcAddress (hDll, "ShowDlg"); // obtain the address of the ShowDlg function.
  
  
If (NULL = addFun)
  
  
{
  
  
MessageBox ("failed to search for functions in DLL ");
  
  
}
  
  
HINSTANCE exe_hinstance = AfxGetResourceHandle (); // obtain the instance handle of the main program
  
  
AfxSetResourceHandle (hDll); // set the main program handle to a DLL instance to use resources in the DLL)
  
  
AddFun (); // call a function
  
  
AfxSetResourceHandle (exe_hinstance); // reset the instance handle of the main program
  
  
FreeLibrary (hDll); // release DLL Resources
  
  
}
 
 

C ++ common DLL class usage

1: Add a new class to the DLL

Class. h file:
 

 
 

  
  
// Export a class (including its methods and attributes)
  
  
Class _ declspec (dllexport) CDllClass {
  
  
Public:
  
  
CDllClass (void );
  
  
Void MSG (const char * const str );
  
  
};
 
 

Class. cpp file:

 
 

  
  
#include "stdafx.h"  
  
  
#include "DllClass.h"  
  
  
 
  
  
CDllClass::CDllClass()  
  
  
{  
  
  
return;  
  
  
}  
  
  
void CDllClass::MSG(const char * const str)  
  
  
{  
  
  
MessageBox(NULL,str,"",MB_OK);  
  
  
} 
 
 

2: copy the compiled DLL files, Lib files, and Class header files to the project directory.

3: Modify the Class header file to convert the dll header file to dllexport and the application file to dllimport)

 
 

  
  
// Import a class (including its methods and attributes)
  
  
Class _ declspec (dllimport) CDllClass {
  
  
Public:
  
  
CDllClass (void );
  
  
Void MSG (const char * const str );
  
  
};
 
 

4: add the Class header file and the reference of the Lib file to the file that calls the class implementation function.

 
 

  
  
# Include "DllClass. h" // introduce the header file, which is an object that can be defined by a program.
  
  
# Pragma comment (lib, "DrawDll. lib") // define a function
 
 

It can be used normally. The above is the introduction to C ++ conventional DLL.