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cpp-mcp - C++ source-intelligence MCP server (setup)

cpp-mcp is a standalone MCP server exposing daslang's C++ source tooling - parse-aware search/outline (via ast-grep) and compile-DB-driven syntax checks - without pulling in the full daslang toolchain. It's the curated cpp/agnostic subset of the daslang MCP server, shipped as a self-contained AOT binary.

It is language/project agnostic: point it at any C/C++ codebase.

What's in the bundle

cpp-mcp/
  bin/cpp-mcp[.exe]            # the server (statically linked; AOT-compiled hot paths)
  utils/mcp/*.das              # server sources (compiled at startup)
  utils/mcp/tools/*.das
  utils/common/*.das           # shared modules the tools require
  utils/mcp/daslang-mcp-msvc.cmd   # Windows vcvars launcher
  tree-sitter-daslang/*.yml    # ast-grep rule files (loaded at runtime)
  daslib/                      # daslang standard library (sources)
  README.md                    # this file

The binary recompiles cpp_main.das (+ daslib) at startup - AOT swaps in the native code, but the sources must be present. getDasRoot() derives the source root from the executable's path, so keep cpp-mcp in bin/ next to the bundled utils/ and daslib/ (or pass --root <bundle-dir>).

Install

  1. Download the bundle for your platform from the releases page and extract it anywhere (e.g. ~/tools/cpp-mcp).

  2. Add a server entry to your MCP client's .mcp.json:

    Linux / macOS - point straight at the binary (clang/gcc find system headers on their own):

    {
  "mcpServers": {
    "cpp-mcp": {
      "command": "/abs/path/to/cpp-mcp/bin/cpp-mcp",
      "defer_loading": false
    }
  }
}

    Windows (MSVC) - launch through the bundled .cmd so cl.exe finds the system headers (compile_commands.json omits them on MSVC; the compiler reads them from the INCLUDE env that vcvars sets):

    {
  "mcpServers": {
    "cpp-mcp": {
      "command": "cmd",
      "args": ["/c", "C:\\abs\\path\\to\\cpp-mcp\\utils\\mcp\\daslang-mcp-msvc.cmd", "cpp-mcp.exe"],
      "defer_loading": false
    }
  }
}

  3. Restart your MCP client and call cpp_status - it reports exactly which dependencies are present and which tools that enables. When checking the compile DB for an external project, pass build_dir (your project's build directory); without it, cpp_status probes the bundle root, not your project.

Tools

Tool Needs
cpp_status nothing - self-diagnosis of the items below
cpp_compile_check a compile_commands.json (CMake CMAKE_EXPORT_COMPILE_COMMANDS=ON); on MSVC, a vcvars env
cpp_build_info a compile_commands.json
cpp_format_file clang-format on PATH + a .clang-format in the project
cpp_grep_usage, cpp_find_symbol, cpp_outline, cpp_goto_definition ast-grep (sg) on PATH
grep_usage, outline ast-grep - for .das files

The compile-DB and status tools work out of the box. The six ast-grep tools are enabled only if sg is on PATH (run cpp_status to confirm); they degrade gracefully when it isn't.

Optional: enable the ast-grep tools

Install ast-grep and ensure sg is on PATH. The bundle already ships the rule files (tree-sitter-daslang/*.yml), so the C/C++ ast-grep tools (cpp_grep_usage, cpp_find_symbol, cpp_outline, cpp_goto_definition) work with just sg installed. The .das tools (grep_usage, outline) additionally need the tree-sitter-daslang grammar + an sgconfig.yml.

Notes

  • --root <dir> overrides source-root autodetection (use when running the binary from outside its bundle layout).
  • The server speaks JSON-RPC over stdio; all diagnostics go to a log file, never stdout (which is the protocol pipe).