Fixing "g++ Not Found" When Debugging Rails in RubyMine on Fedora
TL;DR: If clicking "Debug" in RubyMine on Fedora fails to install debase because of a missing g++ compiler, the standard @development-tools group might not be enough. Run sudo dnf install gcc-c++ make redhat-rpm-config to get the explicit C++ compiler and tools Ruby needs to build native extensions.
I was recently working on a Rails app on my Fedora machine and wanted to step through some code. I fired up RubyMine, set my breakpoints, and clicked the "Debug" button, fully expecting everything to just work.
Instead, RubyMine tried to automatically install the debase and ruby-debug-ide gems—which it needs under the hood to hook into the Ruby process—and threw a massive wall of error text at me.
The core of the failure looked like this:
Building native extensions. This could take a while...
ERROR: Error installing debase-3.0.17.gem:
ERROR: Failed to build gem native extension.
...
/path/to/extconf_common.rb:80:in 'Kernel#`': No such file or directory - g++ (Errno::ENOENT)
My system was essentially complaining that it couldn't find g++, the C++ compiler.
The Initial (Failed) Attempt
My first thought was, "Oh, I must have forgotten to install the base build tools on this machine."
Since I'm on Fedora, I reached for the standard DNF command to pull in the development group:
sudo dnf install @development-tools
(Note: If you're on older versions of Fedora, you might be used to dnf groupinstall "Development Tools", but DNF5 uses the @ syntax or space-separated group install).
It downloaded and installed a bunch of packages. I felt confident, went back to RubyMine, clicked "Debug" again, and... got the exact same No such file or directory - g++ error.
Why Didn't That Work?
When you install Ruby gems that contain native C or C++ extensions (like debase), Ruby doesn't just download a pre-built binary. It actually compiles the raw source code down to machine code directly on your machine so it runs as fast as possible.
While the @development-tools group pulls in a ton of great utilities like git, make, and standard gcc (for C code), it doesn't always explicitly guarantee that the C++ compiler (g++) and Red Hat-specific RPM configuration headers are placed right where Ruby's extconf.rb script is looking for them on a fresh environment.
Without g++ explicitly available in the PATH, the compilation halts immediately.
The Actual Fix
To fix this, I needed to bypass the generic group install and specifically target the C++ toolchain and the Red Hat configuration files that native Ruby extensions rely on.
I ran this command:
sudo dnf install gcc-c++ make redhat-rpm-config
To verify it worked, I double-checked that my shell could now see the compiler:
bash
which g++
# Output: /usr/bin/g++
