C

C support is available natively in Gram.

• Tree-sitter: tree-sitter/tree-sitter-c
• Language Server: clangd/clangd
• Debug Adapter: CodeLLDB (primary), GDB (secondary, not available on Apple silicon)

Clangd: Force detect as C

Clangd out of the box assumes mixed C++/C projects. If you have a C-only project you may wish to instruct clangd to treat all files as C using the -xc flag. To do this, create a .clangd file in the root of your project with the following:

# yaml-language-server: $schema=https://json.schemastore.org/clangd.json
CompileFlags:
  Add: [-xc]

By default clang and gcc will recognize *.C and *.H (uppercase extensions) as C++ and not C and so Gram too follows this convention. If you are working with a C-only project (perhaps one with legacy uppercase pathing like FILENAME.C) you can override this behavior by adding this to your settings:

{
  "file_types": {
    "C": ["C", "H"],
  },
}

Formatting

By default the editor will use the clangd language server for formatting C code like the clang-format CLI tool. To configure this you can add a .clang-format file. For example:

# yaml-language-server: $schema=https://json.schemastore.org/clang-format-21.x.json
---
BasedOnStyle: GNU
IndentWidth: 2
---

See Clang-Format Style Options for a complete list of options.

You can trigger formatting via editor::Format or the editor: format action from the command palette or by adding format_on_save to your Gram settings:

  "languages": {
    "C": {
      "format_on_save": "on",
      "tab_size": 2
    }
  }

Compile Commands

For some projects Clangd requires a compile_commands.json file to properly analyze your project. This file contains the compilation database that tells clangd how your project should be built.

CMake Compile Commands

With CMake, you can generate compile_commands.json automatically by adding the following line to your CMakeLists.txt:

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

After building your project, CMake will generate the compile_commands.json file in the build directory and clangd will automatically pick it up.

Debugging

You can use CodeLLDB or GDB to debug native binaries. (Make sure that your build process passes -g to the C compiler, so that debug information is included in the resulting binary.) See below for examples of debug configurations that you can add to .gram/debug.jsonc.

• CodeLLDB configuration documentation
• GDB configuration documentation

Build and Debug Binary

[
  {
    "label": "Debug native binary",
    "build": {
      "command": "make",
      "args": ["-j8"],
      "cwd": "$GRAM_WORKTREE_ROOT"
    },
    "program": "$GRAM_WORKTREE_ROOT/build/prog",
    "request": "launch",
    "adapter": "CodeLLDB"
  }
]