How to Link Against the MulleObjC-startup Library in Your Project

To link against the MulleObjC-startup library, either use mulle-sde add github:mulle-objc/MulleObjC-startup for automatic dependency management, or manually configure CMake to include the library subdirectory and link the MulleObjC-startup target to your executable.

The mulle-objc/mulleobjc-startup repository provides a static library that supplies the essential __register_mulle_objc_universe entry point and automatically pulls in required runtime dependencies including mulle-atinit and mulle-atexit. Linking this library is mandatory for any executable that needs to bootstrap the Mulle Objective-C runtime. This guide covers both automated and manual integration methods.

Using mulle‑sde to Link MulleObjC‑startup

The mulle‑sde build tool offers the simplest way to integrate the library, automatically handling include paths, compiler flags, and link targets.

Adding the Dependency

Run the following command in your project root to fetch and link the library:

mulle-sde add github:mulle-objc/MulleObjC-startup

This command retrieves the source code, updates your build configuration, and inserts the -lMulleObjC-startup link flag. After adding the dependency, build and run your project normally:

mulle-sde run

The tool ensures that the static library and its transitive dependencies are correctly linked without manual CMake editing.

Manual CMake Integration

For projects requiring explicit control over the build system, you can manually add the library as a CMake subdirectory.

Adding the Library Subdirectory

First, clone the repository or add it as a git submodule, then reference it in your CMakeLists.txt:

cmake_minimum_required(VERSION 3.13)
project(MyApp LANGUAGES C)

# Add the startup library source tree

add_subdirectory(path/to/MulleObjC-startup)

The CMakeLists.txt in the library root defines the static target using the Library macro provided in cmake/share/Library.cmake.

Linking the Target

Connect the startup library to your executable and ensure headers are discoverable:

add_executable(${PROJECT_NAME} main.c)

# Link the static startup library

target_link_libraries(${PROJECT_NAME} PUBLIC MulleObjC-startup)

# Include the public headers

target_include_directories(${PROJECT_NAME}
    PUBLIC
    ${CMAKE_CURRENT_SOURCE_DIR}/path/to/MulleObjC-startup/include
)

This configuration imports the implementation from src/MulleObjC-startup.m, which contains the __register_mulle_objc_universe function that bootstraps the Objective-C universe.

Required Headers and Implementation Details

Regardless of the integration method, source files that interact with the startup routine must import the public header:

#import <MulleObjC-startup/MulleObjC-startup.h>

The library exports the __register_mulle_objc_universe symbol defined in src/MulleObjC-startup.m, which initializes the runtime environment. The build definition in CMakeLists.txt uses cmake/share/Library.cmake to create the compile and link targets properly.

When using mulle‑sde, these includes are configured automatically. In manual setups, verify that path/to/MulleObjC-startup/include is in your compiler's search path.

Summary

• MulleObjC-startup is a static library that provides the __register_mulle_objc_universe entry point required to bootstrap the Mulle Objective-C runtime.
• Use mulle-sde add github:mulle-objc/MulleObjC-startup for automatic linking and header configuration.
• For manual CMake integration, use add_subdirectory followed by target_link_libraries(your_exe PUBLIC MulleObjC-startup).
• Include <MulleObjC-startup/MulleObjC-startup.h> in source files that need access to the startup routine.
• The implementation resides in src/MulleObjC-startup.m, with build logic defined in the root CMakeLists.txt and cmake/share/Library.cmake.

Frequently Asked Questions

What is the purpose of the MulleObjC-startup library?

The library provides the __register_mulle_objc_universe function that initializes the Objective-C runtime universe. It also links against mulle-atinit and mulle-atexit to handle constructor and destructor priorities, ensuring the runtime is ready before your application code executes.

Can I use MulleObjC-startup with build systems other than CMake?

While the repository is optimized for CMake and mulle‑sde, you can adapt the build logic for other systems. The critical requirement is compiling src/MulleObjC-startup.m and linking the resulting static library with your executable, then ensuring the header path include/ is available to the compiler.

Why does my executable fail to link without MulleObjC-startup?

The Mulle Objective-C runtime requires a specific entry point to register the universe before main() executes. Without linking against MulleObjC-startup, the __register_mulle_objc_universe symbol remains undefined, causing linker errors or runtime crashes when attempting to send Objective-C messages.

Where are the public headers located in the repository?

The public interface is located at include/MulleObjC-startup/MulleObjC-startup.h in the source tree. When using mulle‑sde, this path is added to your include search paths automatically. For manual CMake setups, you must explicitly add the include directory to your target's include directories.

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