Visual C++ and MFC Programming 2nd Edition

Index Visual C++ and MFC Fundamentals

22.4.2..Fundamentals of a DLL......................................................................

We have mentioned that a DLL is created as a project that contains at least one source

file and this source file should present an entry-point. After creating the DLL, you will

build and distribute it so other programs can use it. When building it, you must create a

library file that will accompany the DLL. This library file will be used by other programs

to import what is available in the DLL:

When the import library is created, it contains information about where each available

function is included in the DLL and can locate it. When an application needs to use a

function contained in the DLL, it presents its request to the import library. The import

library checks the DLL for that function. If the function exists, the client program can use

it. If it does not, the library communicates this to the application and the application

presents an error.

Normally, the import library is created when building the DLL but you must provide a

mechanism for the compiler to create it. There are two main ways you do this. You can

use a calling convention that allows the compiler to detect what function will be

accessible to the clients of the DLL. In this case, each one of these functions will start

with the _declspec modifier. When creating the DLL, the _declspec modifier must take

as argument the dllexport keyword.

The functions do not have to be included in the main file that contains the entry-point; it

may simply be convenient to do it that way.

Practical Learning: Creating a DLL

1. To start a new project, on the main menu, click File -> Project...


2. In the New Project dialog box, in the Project Type list, select Visual C++. In the
   Templates list, click Win32 Project


3. In the Name edit box, type MomentOfInertia

DLL

Import

Library

Client

Application