C Compiler

Compile C from TypeScript

Use cc from bun:ffi to compile C source and call it immediately:

import { cc } from "bun:ffi";

const { symbols } = cc({
  source: "./math.c",
  symbols: {
    add: { args: ["int", "int"], returns: "int" },
  },
});

console.log(symbols.add(3, 4)); // 7

// math.c
int add(int a, int b) {
  return a + b;
}

No Makefile, no cargo, no node-gyp. The C code is compiled on first use and linked into the running process.

Define symbols

The symbols object maps C function names to their FFI signatures:

const { symbols } = cc({
  source: "./image.c",
  symbols: {
    grayscale: {
      args: ["ptr", "int", "int"],
      returns: "int",
    },
    resize: {
      args: ["ptr", "int", "int", "ptr", "int", "int"],
      returns: "int",
    },
  },
});

Each entry specifies argument types and the return type using the same FFI type system (int, ptr, cstring, etc.).

Link system libraries

Pass library to link against installed shared libraries:

const { symbols } = cc({
  source: "./sqlite_query.c",
  symbols: {
    query_version: { args: [], returns: "cstring" },
  },
  library: ["sqlite3"],
  define: { NDEBUG: "1" },
});

• library — link flags (e.g. ["sqlite3"] links -lsqlite3)
• define — preprocessor defines passed to the compiler
• flags — additional compiler flags (include paths, warnings)

N-API interop

For functions that need to return JavaScript values (strings, objects, arrays), use N-API:

const { symbols } = cc({
  source: "./greeting.c",
  symbols: {
    greet: { args: ["napi_env"], returns: "napi_value" },
  },
});

console.log(symbols.greet()); // "Hello from C!"

#include <node/node_api.h>

napi_value greet(napi_env env) {
  napi_value result;
  napi_create_string_utf8(env, "Hello from C!", NAPI_AUTO_LENGTH, &result);
  return result;
}

N-API allows full interop with JavaScript object types without manual serialization.