GCC

Catalog v8.

Installs GCC for C and C++ with GDB, clangd and the common build tools, and lets compilers find the libraries of [nixos] packages.

Select

[toolchains]
gcc = "15"

Choose the line in the [toolchains] table of limanix.toml and apply the change. Add Clang in the same table for a second compiler.

Versions

Value	GCC	Notes
16	16.x
15	15.x	Recommended
14	14.x

Lines come from the base Nixpkgs revision and receive its updates with each catalog release. gcc, g++, cc and c++ run the selected line, also when Go or Rust install their own GCC.

Use

Inside the VM:

cc -o hello hello.c
c++ -std=c++20 -o hello hello.cpp

The module also installs GNU Binutils, make, CMake, Ninja, Meson, pkg-config, Autoconf, Automake, Libtool, M4 and GDB:

cmake -B build -G Ninja
cmake --build build

Native libraries

Add a library to [nixos] packages and build against it:

[nixos]
packages = ["openssl", "libpq"]

The module installs the development files of [nixos] packages and links their headers, pkg-config files, CMake packages and Autoconf macros into the system profile /run/current-system/sw. GCC and Clang search its headers and libraries after their own, so cc -o app app.c -lssl needs no extra flags. Programs they link search there last for libraries when they run. pkg-config, CMake and aclocal find the same packages.

Python packages with C extensions, node-gyp addons and crates with -sys build this way. node-gyp also needs Python: select python next to nodejs in [toolchains].

Editor support

The module installs clangd for C and C++ files in editors that support the Language Server Protocol; AstroNvim starts it. clangd reads compile_commands.json, which CMake writes with -DCMAKE_EXPORT_COMPILE_COMMANDS=ON, and asks the compiler for its include paths.

Configuration and integration

Boundary	Contract
Public capability	lmx.capabilities.languageSupport.tools.clangd; C, C++ and CMake parsers
Settings	environment.extraOutputsToInstall = [ "dev" ]; links /include, /share/aclocal, /share/cmake and /share/pkgconfig; PKG_CONFIG_PATH, CMAKE_PREFIX_PATH and ACLOCAL_PATH point to /run/current-system/sw
Compilers	cc, c++, gcc and g++ add -idirafter /run/current-system/sw/include and -L/run/current-system/sw/lib; dynamic links get /run/current-system/sw/lib as their last RUNPATH entry
Integration	Clang imports this module; Go and Rust keep their GCC behind the selected line
Services	No daemon

Corner cases

Case	Behavior or next step
A header is missing	Add the library to [nixos] packages; its development files come with it
A built program misses a library after its package was removed	Add the package back, or rebuild the program
CMake does not find a package that keeps its CMake files in another share directory, such as Eigen	Use pkg-config, or set <Package>_DIR