When attempting to build OpenCV on Ubuntu, developers sometimes encounter a frustrating error: "Undefined reference to g_memdup2." This issue often arises due to a missing or misconfigured dependency, specifically related to the GLib library. In this article, we will explore the problem in detail and provide a step-by-step guide to resolve it.
Original Problem Code Snippet
$ cmake ..
$ make
Upon executing these commands, you may come across an error message similar to this:
undefined reference to `g_memdup2'
Understanding the Problem
The g_memdup2 function is part of the GLib library, which is a low-level core library that forms the basis for projects like GTK and GNOME. The "undefined reference" error suggests that the linker cannot find the implementation of the g_memdup2 function during the build process. This could be due to a variety of reasons, such as an outdated version of GLib or an improper installation of OpenCV.
Analyzing the Issue
When building OpenCV from source, it’s crucial to ensure that all dependencies are correctly installed and configured. The error related to g_memdup2 indicates a linkage problem with GLib, which could stem from:
- Outdated GLib Version: The function
g_memdup2was introduced in GLib version 2.36. If your system has an older version, the reference will not be resolved. - Incomplete Installation: If the GLib development files were not installed, the compiler won't find the necessary headers and libraries.
- Incorrect CMake Configuration: Sometimes, CMake might not locate the GLib library properly, leading to the undefined reference error.
Step-by-Step Solution
To resolve the undefined reference error, follow these steps:
1. Install the Required Dependencies
Make sure to have the required libraries installed. You can do this by executing the following command in the terminal:
sudo apt-get update
sudo apt-get install build-essential cmake git libgtk-3-dev libatlas-base-dev gfortran python3-dev libglib2.0-dev
2. Check GLib Version
Verify the version of GLib installed on your system:
pkg-config --modversion glib-2.0
Ensure that the version is 2.36 or higher. If it is not, you may need to upgrade GLib:
sudo apt-get install libglib2.0-dev
3. Clean and Rebuild OpenCV
If you are still facing issues after verifying dependencies, clean your OpenCV build directory and reconfigure the build:
cd /path/to/opencv/build
rm -rf *
cmake ..
make -j4
4. Verify the Build
After running the build commands, check to see if the error has been resolved. You should no longer see the "undefined reference" error.
Additional Tips and Resources
- Use Docker: If you frequently encounter issues building OpenCV on Ubuntu, consider using a Docker container that already has OpenCV set up. This can save time and reduce configuration headaches.
- Official OpenCV Documentation: Always refer to the OpenCV installation guide for the most up-to-date instructions.
- Community Forums: If you encounter persistent issues, don't hesitate to seek help from forums such as Stack Overflow or the OpenCV GitHub page.
Conclusion
Building OpenCV on Ubuntu can sometimes come with challenges, such as the "undefined reference to g_memdup2" error. However, with the right approach and by ensuring all dependencies are correctly installed, you can successfully resolve this issue and continue with your development. Following the steps outlined above will help guide you through the process, so you can leverage the powerful capabilities of OpenCV in your projects.
Useful Resources
By following this guide, developers can troubleshoot and resolve common issues while building OpenCV on Ubuntu, ensuring a smoother and more productive experience.
