VC ++ generates DLL and uses DLL in QT

1. generate DLL

 

1. Create a DLL Project

You can use multiple methods to generate a DLL. In vs, create an empty project, select Win32 console application, and modify the project properties after the new project is created: Change the generated EXE to the generated DLL

 

2.Source code:

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# include "stdafx. H "
# ifdef _ cplusplus // if used by C ++ Code
extern" C "{// We need to export the C interface
# endif
_ declspec (dllexport) void mysub (int x, int y, int * z)
{< br> * z = x-y;
}< BR ># ifdef _ cplusplus
}< BR ># endif
# include "stdafx. H "

# Ifdef _ cplusplus // if used by C ++ code
Extern "C" {// We need to export the C interface
# Endif
_ Declspec (dllexport) void mysub (int x, int y, int * z)
{
* Z = x-y;
}
# Ifdef _ cplusplus
}
# Endif

 

 

3. Compile the connection and generate the XYZ. dll file.

 

Ii. Use DLL

 

1. Create a project

Create a New GUI application in QT creator, and place two Pushbutton (load and quit) on the left side of the label on the form ).

Use the quit clicked () signal to bind the close () slot, and load the clicked () signal to the load () slot.

2. SourceCode:

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Void mainwindow: load ()
{
Int A = 1, B = 2, c = 6;
Typedef void (* myfun) (INT, Int, int *);
Qlibrary lib ("XYZ ");
Qstring qss;
If (Lib. Load ())
{
Myfun fun1 = (myfun) Lib. Resolve ("mysub"); // use resolve to parse the fun1 Function
If (fun1) // if the resolution is successful, the operation is performed and related information is prompted.
{
Fun1 (a, B, & C );
Qss = tr ("DLL success load! /N 1 + 2 = ") + qstring: Number (C, 10 );

}
}
Else
{
Qss = tr ("not found DLL! ");
}
UI-> label-> settext (qss );
}
Void mainwindow: load ()
{
Int A = 1, B = 2, c = 6;
Typedef void (* myfun) (INT, Int, int *);
Qlibrary lib ("XYZ ");
Qstring qss;
If (Lib. Load ())
{
Myfun fun1 = (myfun) Lib. Resolve ("mysub"); // use resolve to parse the fun1 Function
If (fun1) // if the resolution is successful, the operation is performed and related information is prompted.
{
Fun1 (a, B, & C );
Qss = tr ("DLL success load! /N 1 + 2 = ") + qstring: Number (C, 10 );

}
}
Else
{
Qss = tr ("not found DLL! ");
}
UI-> label-> settext (qss );
}
 

 

PS: the QT help document provides the following description:

 

Void * qlibrary: Resolve (const char * symbol)

 

The symbol must be exported as a C function from the library. this means that the function must be wrapped in an extern "C" if the library is compiled with a C ++ compiler. on Windows you must also explicitly export the function from the DLL using the_declspec (dllexport) compiler Directive, for example:

For a description of _ declspec, see the http://blog.csdn.net/lw02nju/archive/2009/07/22/4370002.aspx

Extern "C" my_export int AVG (int A, int B)
{
Return (A + B)/2;
} With my_export defined

# Ifdef q_ws_win
# Define my_export _ declspec (dllexport)
# Else
# Define my_export
# Endif

This article from the csdn blog, reproduced please indicate the source: http://blog.csdn.net/marsterran/archive/2010/03/26/5419706.aspx