In this article, we will delve into a common error that developers may encounter when compiling a program with GLAD and SDL2 using g++: the “undefined reference to symbol ‘dlclose@@GLIBC_2.2.5′” error. This error can occur even when the “-ldl” flag is included in the compilation command. We will explore the root cause of this error and provide a detailed guide on how to fix it.
To fix the "undefined reference to symbol ‘dlclose@@GLIBC_2.2.5’" error when using g++, adjust the order of the libraries in the compilation command. Specifically, place the "-ldl" flag after the "-lSDL2" flag. This ensures that the dynamic linking loader library (libdl) is correctly linked. Recompile your program after making this change.
Understanding the Error
The error message “undefined reference to symbol ‘dlclose@@GLIBC_2.2.5′” indicates that the linker is unable to find a reference to the symbol ‘dlclose@@GLIBC_2.2.5’. This error usually occurs when the dynamic linking loader library (libdl) is not correctly linked during the compilation process. The “-ldl” flag is used to link this library, but the error can still occur if the flag is not placed correctly in the command.
The Role of the -ldl Flag
The “-ldl” flag is used in the g++ command to link the dynamic linking loader library (libdl). This library provides the necessary functions for the program to dynamically load and call shared library code during runtime. The ‘dlclose’ function, which is the subject of the error, is one such function provided by libdl.
The Importance of Library Order in GCC
One of the main reasons for the occurrence of this error is the order in which the libraries are linked. The order of the libraries can sometimes cause errors in GCC. This is because the linker processes the libraries and object files in the order they are specified in the command. If a library that depends on another library is processed before the library it depends on, the linker may not be able to resolve all symbols, leading to errors.
How to Fix the Error
To fix this error, you need to adjust the order of the libraries in the g++ command. Specifically, the “-ldl” flag should be placed after the “-lSDL2” flag. Here is an example of how to adjust the command:
g++ -o out/cpptest bin/src/MainTest.o bin/src/main.o -L/usr/local/lib -Lbin/lib -lm -lGL -lGLU -lX11 -lpthread -lXi -lXrandr -lXxf86vm -lXinerama -lXcursor -lrt -lglad -lSDL2 -ldl -pthreadIn this command:
-o out/cpptestspecifies the output file name.bin/src/MainTest.o bin/src/main.oare the object files to be linked.-L/usr/local/lib -Lbin/libspecify the paths to search for libraries.-lm -lGL -lGLU -lX11 -lpthread -lXi -lXrandr -lXxf86vm -lXinerama -lXcursor -lrt -lglad -lSDL2 -ldl -pthreadare the libraries to be linked. The-ldlflag has been moved after the-lSDL2flag to ensure the correct order.
After adjusting the command, recompile your program. If the error was due to the order of the libraries, this should resolve the issue.
Checking for Missing Libraries
If adjusting the order of the libraries does not resolve the error, you should check if the library “libglad.a” is present in the specified path “bin/lib/libglad.a”. If the library is missing, you will need to obtain it and place it in the correct location.
Conclusion
The “undefined reference to symbol ‘dlclose@@GLIBC_2.2.5′” error can be a stumbling block when compiling programs with g++. However, by understanding the role of the “-ldl” flag and the importance of the order of libraries in GCC, you can easily fix this error. Always remember to recompile your program after making any changes to the compilation command.
For more information on the order in which libraries are linked and potential errors in GCC, you can refer to the following Stack Overflow post: Why does the order in which libraries are linked sometimes cause errors in GCC?
This error indicates that the linker is unable to find a reference to the symbol ‘dlclose@@GLIBC_2.2.5’. It usually occurs when the dynamic linking loader library (libdl) is not correctly linked during the compilation process.
To fix this error, you need to adjust the order of the libraries in the g++ command. Specifically, the "-ldl" flag should be placed after the "-lSDL2" flag. After adjusting the command, recompile your program.
The order of the libraries matters in GCC because the linker processes them in the order they are specified in the command. If a library that depends on another library is processed before the library it depends on, the linker may not be able to resolve all symbols, leading to errors.
If adjusting the order of the libraries doesn’t resolve the error, you should check if the library "libglad.a" is present in the specified path "bin/lib/libglad.a". If the library is missing, you will need to obtain it and place it in the correct location.
Yes, you can refer to the following Stack Overflow post for more information: Why does the order in which libraries are linked sometimes cause errors in GCC?
