Walkthrough: Create and use a static library

This step-by-step walkthrough shows how to create a static library (.lib file) for use with C++ apps. Using a static library is a great way to reuse code. Rather than reimplementing the same routines in every app that requires the functionality, you write them one time in a static library and then reference it from the apps. Code linked from a static library becomes part of your app—you don't have to install another file to use the code.

This walkthrough covers these tasks:

• Create a static library project

• Add a class to the static library

• Create a C++ console app that references the static library

• Use the functionality from the static library in the app

• Run the app

Prerequisites

An understanding of the fundamentals of the C++ language.

Create a static library project

The instructions for how to create the project vary depending on your version of Visual Studio. To see the documentation for your preferred version of Visual Studio, use the Version selector control. It's found at the top of the table of contents on this page.

Add a class to the static library

To add a class to the static library

1. To create a header file for a new class, right-click to open the shortcut menu for the MathLibrary project in Solution Explorer, and then choose Add > New Item.

2. In the Add New Item dialog box, select Visual C++ > Code. In the center pane, select Header File (.h). Specify a name for the header file—for example, MathLibrary.h—and then choose the Add button. A nearly blank header file is displayed.

3. Add a declaration for a class named Arithmetic to do common mathematical operations such as addition, subtraction, multiplication, and division. The code should resemble:

   // MathLibrary.h
   #pragma once
   
   namespace MathLibrary
   {
       class Arithmetic
       {
       public:
           // Returns a + b
           static double Add(double a, double b);
   
           // Returns a - b
           static double Subtract(double a, double b);
   
           // Returns a * b
           static double Multiply(double a, double b);
   
           // Returns a / b
           static double Divide(double a, double b);
       };
   }
   

4. To create a source file for the new class, open the shortcut menu for the MathLibrary project in Solution Explorer, and then choose Add > New Item.

5. In the Add New Item dialog box, in the center pane, select C++ File (.cpp). Specify a name for the source file—for example, MathLibrary.cpp—and then choose the Add button. A blank source file is displayed.

6. Use this source file to implement the functionality for class Arithmetic. The code should resemble:

   // MathLibrary.cpp
   // compile with: cl /c /EHsc MathLibrary.cpp
   // post-build command: lib MathLibrary.obj
   
   #include "MathLibrary.h"
   
   namespace MathLibrary
   {
       double Arithmetic::Add(double a, double b)
       {
           return a + b;
       }
   
       double Arithmetic::Subtract(double a, double b)
       {
           return a - b;
       }
   
       double Arithmetic::Multiply(double a, double b)
       {
           return a * b;
       }
   
       double Arithmetic::Divide(double a, double b)
       {
           return a / b;
       }
   }
   

7. To build the static library, select Build > Build Solution on the menu bar. The build creates a static library, MathLibrary.lib, that can be used by other programs.

   Note

   When you build on the Visual Studio command line, you must build the program in two steps. First, run cl /c /EHsc MathLibrary.cpp to compile the code and create an object file that's named MathLibrary.obj. (The cl command invokes the compiler, Cl.exe, and the /c option specifies compile without linking. For more information, see /c (Compile Without Linking).) Second, run lib MathLibrary.obj to link the code and create the static library MathLibrary.lib. (The lib command invokes the Library Manager, Lib.exe. For more information, see LIB Reference.)

Create a C++ console app that references the static library

Use the functionality from the static library in the app

To use the functionality from the static library in the app

1. Before you can use the math routines in the static library, you must reference it. Open the shortcut menu for the MathClient project in Solution Explorer, and then choose Add > Reference.

2. The Add Reference dialog box lists the libraries that you can reference. The Projects tab lists the projects in the current solution and any libraries they reference. Open the Projects tab, select the MathLibrary check box, and then choose the OK button.

3. To reference the MathLibrary.h header file, you must modify the included directories path. In Solution Explorer, right-click on MathClient to open the shortcut menu. Choose Properties to open the MathClient Property Pages dialog box.

4. In the MathClient Property Pages dialog box, set the Configuration drop-down to All Configurations. Set the Platform drop-down to All Platforms.

5. Select the Configuration Properties > C/C++ > General property page. In the Additional Include Directories property, specify the path of the MathLibrary directory, or browse for it.

   To browse for the directory path:

   1. Open the Additional Include Directories property value drop-down list, and then choose Edit.

   2. In the Additional Include Directories dialog box, double-click in the top of the text box. Then choose the ellipsis button (...) at the end of the line.

   3. In the Select Directory dialog box, navigate up a level, and then select the MathLibrary directory. Then choose the Select Folder button to save your selection.

   4. In the Additional Include Directories dialog box, choose the OK button.

   5. In the Property Pages dialog box, choose the OK button to save your changes to the project.

6. You can now use the Arithmetic class in this app by including the #include "MathLibrary.h" header in your code. Replace the contents of MathClient.cpp with this code:

   // MathClient.cpp
   // compile with: cl /EHsc MathClient.cpp /link MathLibrary.lib
   
   #include <iostream>
   #include "MathLibrary.h"
   
   int main()
   {
       double a = 7.4;
       int b = 99;
   
       std::cout << "a + b = " <<
           MathLibrary::Arithmetic::Add(a, b) << std::endl;
       std::cout << "a - b = " <<
           MathLibrary::Arithmetic::Subtract(a, b) << std::endl;
       std::cout << "a * b = " <<
           MathLibrary::Arithmetic::Multiply(a, b) << std::endl;
       std::cout << "a / b = " <<
           MathLibrary::Arithmetic::Divide(a, b) << std::endl;
   
       return 0;
   }
   

7. To build the executable, choose Build > Build Solution on the menu bar.

Run the app

To run the app

1. Make sure that MathClient is selected as the default project. To select it, right-click to open the shortcut menu for MathClient in Solution Explorer, and then choose Set as StartUp Project.

2. To run the project, on the menu bar, choose Debug > Start Without Debugging. The output should resemble:

   a + b = 106.4
   a - b = -91.6
   a * b = 732.6
   a / b = 0.0747475
   

See also

Walkthrough: Creating and Using a Dynamic Link Library (C++)