# How to Integrate MulleObjC-startup into Your Project Using mulle-sde > Effortlessly integrate MulleObjC-startup into your project use mulle-sde. Learn to initialize add and build your project with simple commands for automatic dependency linking. - Repository: [mulle-objc/mulleobjc-startup](https://github.com/mulle-objc/mulleobjc-startup) - Tags: how-to-guide - Published: 2026-03-07 --- **To integrate MulleObjC-startup using mulle-sde, initialize your project with `mulle-sde init`, add the library with `mulle-sde add github:mulle-objc/MulleObjC-startup`, and build with `mulle-sde run` to automatically link the startup routines and runtime dependencies.** The `mulle-objc/mulleobjc-startup` repository provides the essential `__register_mulle_objc_universe` symbol and runtime initialization helpers required for any MulleObjC application. When you integrate MulleObjC-startup into your project using mulle-sde, the tool automatically resolves transitive dependencies like MulleObjC and mulle-core, then configures CMake to link the static library correctly. ## Initializing Your mulle-sde Project Before adding the startup library, you need a working mulle-sde project structure. The tool generates the necessary CMake scaffolding and dependency management files. ### Creating a New Executable Project Run the initialization command with the appropriate craft (template) for Objective-C development: ```bash mulle-sde init -d my-project -m mulle-objc/objc-developer executable cd my-project mulle-sde vibecoding on # optional: enables colourful output ``` This creates the `my-project` directory with a [`CMakeLists.txt`](https://github.com/mulle-objc/mulleobjc-startup/blob/main/CMakeLists.txt) pre-configured for MulleObjC development and a `mulle-sde` environment ready to manage dependencies. ### Configuring an Existing Project If you have an existing CMake project, ensure your [`CMakeLists.txt`](https://github.com/mulle-objc/mulleobjc-startup/blob/main/CMakeLists.txt) includes the mulle-sde integration lines. The tool looks for these markers to inject dependency configurations automatically when you add libraries. ## Adding MulleObjC-startup to Your Dependencies The core integration step uses the `mulle-sde add` command to fetch and register the startup library. Execute the following from your project root: ```bash mulle-sde add github:mulle-objc/MulleObjC-startup ``` This single command performs three critical operations: 1. **Clones the repository** into your project's stash directory (`.mulle/var/${MULLE_HOST}/stash`), fetching the source code including `src/MulleObjC-startup.m`. 2. **Registers the dependency graph**, parsing the library's requirements and automatically pulling in `mulle-atinit`, `mulle-atexit`, and the core MulleObjC runtime. 3. **Updates CMakeLists.txt**, injecting the necessary `target_link_libraries` entries to link the static `MulleObjC-startup` library and its transitive dependencies. The `src/MulleObjC-startup.m` file contains the implementation of `__register_mulle_objc_universe`, the entry point that initializes the Objective-C universe before your `main` function executes. ## Including Headers and Writing Startup Code Once the dependency is added, you can reference the startup header in your source files to ensure proper initialization sequencing. Add the import statement to your main source file: ```c #import ``` This header exposes the `__register_mulle_objc_universe` declaration and any auxiliary macros required for runtime initialization. You typically do not need to call this function manually—the startup library uses constructor attributes (via `mulle-atinit`) to execute it automatically before `main`. ### Complete Example Here is a minimal executable that uses the startup library to initialize the MulleObjC runtime: ```c /* main.m – minimal executable using MulleObjC-startup */ #import #import int main(void) { // The universe is already registered by the startup library. // You can now create and use Objective‑C objects. MulleObjCClass *cls = mulle_objc_class_lookup( "NSObject" ); id obj = mulle_objc_object_new( cls ); // Use your object... mulle_objc_object_release( obj ); return 0; } ``` ## Building and Running Your Application With the dependency integrated and source files written, use mulle-sde to build and execute. Run the build command from your project root: ```bash mulle-sde run ``` This command invokes CMake, which links the static `MulleObjC-startup` library together with the MulleObjC runtime and the `mulle-atinit`/`mulle-atexit` helpers. The resulting binary automatically calls the startup routine defined in `src/MulleObjC-startup.m` before entering your `main` function, ensuring the Objective-C universe is fully initialized. ## Summary - **Use `mulle-sde add github:mulle-objc/MulleObjC-startup`** to automatically fetch the library and resolve transitive dependencies like `mulle-atinit` and `mulle-atexit`. - **The startup library provides `__register_mulle_objc_universe`** in `src/MulleObjC-startup.m`, which initializes the Objective-C runtime before `main` executes. - **Include ``** in your source files to ensure proper initialization sequencing. - **Build with `mulle-sde run`** to link the static library and execute your binary with the runtime fully configured. ## Frequently Asked Questions ### What does MulleObjC-startup actually do? MulleObjC-startup provides the `__register_mulle_objc_universe` symbol that initializes the Objective-C runtime universe before your `main` function executes. According to the mulle-objc/mulleobjc-startup source code, the implementation in `src/MulleObjC-startup.m` uses constructor attributes via `mulle-atinit` to ensure automatic registration, eliminating the need for manual runtime setup in your application code. ### Can I use MulleObjC-startup without mulle-sde? While technically possible, manual integration is strongly discouraged because MulleObjC-startup depends on complex transitive dependencies including `mulle-atinit`, `mulle-atexit`, and the core MulleObjC runtime. The `mulle-sde` tool automatically resolves these dependencies, configures CMake with correct linking order, and manages the stash directory structure. Manual configuration would require replicating this dependency resolution and build system integration by hand. ### Where is the startup routine defined in the source code? The startup routine is defined in `src/MulleObjC-startup.m` within the mulle-objc/mulleobjc-startup repository. This file implements the `__register_mulle_objc_universe` function, which serves as the entry point for runtime initialization. The function is marked with constructor attributes that ensure execution during program startup, before control reaches the `main` function of your executable. ### How do I verify that the universe registration succeeded? You can verify successful registration by checking the return value of runtime functions in your `main` function after including ``. If the universe failed to register, calls like `mulle_objc_class_lookup` would return `NULL` or cause runtime errors. Successful execution of `mulle-sde run` without linker errors regarding missing `__register_mulle_objc_universe` symbols also confirms correct integration, as the build system would fail to link if the startup library were missing.