Cpp Modules

This is your reference when touching C++20 modules, which are still rough around the edges despite being standardized. It walks through named modules versus header units, module partitions, and the Global Module Fragment trick for preserving macro access. The CMake section is solid (requires 3.28+ with FILE_SET CXX_MODULES) and the compiler flag examples for Clang and GCC will save you from the usual "module not found" spiral. The error table is honest about common gotchas like stale BMI caches and ODR violations across partitions. Use this when migrating from headers or debugging why your build system can't find the precompiled module files.

skills.sh installs: 597
GitHub stars: 279
last updated: Aug 21, 2026

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Install

$ npx -y skills add mohitmishra786/low-level-dev-skills --skill cpp-modules --agent claude-code

Installs into .claude/skills of the current project.

Files

C++20 Modules

Purpose

Guide agents through authoring, building, and debugging C++20 modules: named modules vs header units, module partitions, CMake integration, compiler-specific flags, and interoperability with legacy headers.

Triggers

"How do I write a C++20 module?"
"How do I import a module in CMake?"
"What's the difference between a named module and a header unit?"
"My module gives 'cannot find module' errors"
"How do I use C++20 modules with Clang?"
"How do I migrate from headers to modules?"

Workflow

1. Module concepts overview

C++20 module kinds:
├── Named module interface unit  (.cppm / .ixx)  — exports declarations
├── Module implementation unit   (.cpp)           — defines module members
├── Module partition             (.cppm)          — internal module subdivision
└── Header unit                  (any header)     — import a legacy header as module

Named modules are the primary target. Header units are a bridge for legacy code. Avoid Global Module Fragment unless required for macro access.