Opengl Glut

Understanding the GLUT Exit Redefinition Error in OpenGL

When diving into OpenGL programming, especially with the GLUT library, you may encounter a frustrating issue known as the GLUT exit redefinition error. This is particularly common if you are using Microsoft Visual Studio 2005 or its Express Edition. But what is the cause of this error, and how can you address it effectively? Let’s explore the problem and its solution in detail.

The Problem: What Is the GLUT Exit Redefinition Error?

You might see an error message similar to the following when compiling your code:

1>c:\program files\microsoft visual studio 8\vc\include\stdlib.h(406) : error C2381: 'exit' : redefinition; __declspec(noreturn) differs
1>        c:\program files\microsoft visual studio 8\vc\platformsdk\include\gl\glut.h(146) : see declaration of 'exit'

Why Does This Error Occur?

This error happens because:

  • The stdlib.h file included with recent versions of Microsoft Visual Studio has a different definition for the exit() function.
  • This definition conflicts with the one provided in glut.h, leading to a redefinition issue.

In simple terms, both header files are trying to define exit(), but they specify it in slightly different ways, which confuses the compiler.

The Solution: Fixing the Redefinition Error

Fortunately, there is a straightforward way to resolve this issue. Here’s how you can do it:

Step-by-Step Guide

  1. Rearrange Your Include Statements: Make sure that you include stdlib.h before glut.h in your code. This should look like:

    #include <stdlib.h>
#include <GL/glut.h>

  2. Compile Your Code: After you have made the changes to the include order, try recompiling your program. The error should no longer appear, allowing your OpenGL program to compile successfully.

Why This Works

By including stdlib.h before glut.h, you ensure that the compiler sees the correct definition of exit() first. As a result, this prevents the conflicting definitions from causing an issue during compilation.

Conclusion

Encountering the GLUT exit redefinition error can be a roadblock for any OpenGL programmer, but with a simple adjustment to your code’s include order, you can quickly overcome it. Just remember to always place stdlib.h before glut.h, and you’ll avoid this common pitfall.

Now, next time you are programming with OpenGL and GLUT, you can do so without worrying about the exit redefinition error, allowing you to focus on creating amazing graphics and applications.