When developing R packages, encountering errors can be frustrating, particularly when these errors seem to arise from the depths of the build process. One common error that many R developers face is the "ld: cannot find -lgfortran" message. This article will walk you through understanding this problem and how to resolve it effectively.
Understanding the Problem
The error message "ld: cannot find -lgfortran" typically indicates that the linker (ld) cannot locate the GFortran library required for linking during the compilation of your R package. GFortran is the GNU Fortran compiler, and it is necessary for compiling code that relies on Fortran libraries.
Scenario Setup
You are trying to build an R package that contains compiled Fortran code, and you encounter the following error message when running R CMD INSTALL:
ld: cannot find -lgfortran
This error often occurs when the GFortran library is not installed on your system or when its path is not configured correctly.
Original Code Context
The R package includes Fortran code that is being compiled, and you may have a Makevars file like this:
PKG_CFLAGS =
PKG_FCFLAGS =
PKG_LIBS = -lgfortran
This snippet indicates that the package relies on GFortran for linking the Fortran code.
Analyzing the Error
What Causes the Error?
There are several reasons you might face this error:
- GFortran Not Installed: The most common reason is that GFortran is simply not installed on your machine.
- Incorrect Path: The library may be installed, but the linker cannot find it because it’s not in the expected path.
- Incompatible Versions: Sometimes, having multiple compiler versions can cause issues if they are not compatible.
Checking GFortran Installation
First, verify if GFortran is installed on your system. You can do this by executing the following command in your terminal:
gfortran --version
If it is installed, the command will return the version information. If it is not installed, you will need to install it.
Installation Instructions
For Ubuntu/Debian-based Systems
You can install GFortran using the following command:
sudo apt-get update
sudo apt-get install gfortran
For macOS
If you're using macOS, you can install GFortran via Homebrew:
brew install gcc
This installs GFortran as part of the GCC package.
Setting the Correct Path
If GFortran is installed, but you’re still encountering the error, ensure that the library path is correctly configured. You may need to add the library path to your LD_LIBRARY_PATH environment variable:
export LD_LIBRARY_PATH=/path/to/your/gfortran/library:$LD_LIBRARY_PATH
You can find out where GFortran libraries are located using:
find /usr/lib -name "libgfortran*"
Make sure to adjust the path accordingly.
Conclusion
In summary, the "ld: cannot find -lgfortran" error during the R package build process typically stems from issues related to the GFortran library. By confirming that GFortran is installed, checking the installation paths, and ensuring your environment variables are correctly set, you can resolve this issue and successfully build your R package.
Additional Resources
- R Packages by Hadley Wickham: A comprehensive guide to R package development.
- GNU Fortran Documentation: Official documentation for GFortran, including installation details.
By following the steps outlined in this article, you should be able to overcome the "ld: cannot find -lgfortran" error and continue your development work without hindrance.
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