linkedit

The ld64 linker, commonly referred to as linkedit, is the default linker used in macOS and iOS development. It is responsible for combining object files and libraries into a single executable program or shared library. Linkedit processes the output of the compiler, such as object files containing machine code and relocation information, and resolves symbol references between different compilation units. It also handles the allocation of memory addresses for code and data segments, and creates the final executable image that the operating system can load and run.

Linkedit is a command-line tool but is typically invoked by higher-level build tools like Xcode. It understands various executable formats, most notably the Mach-O format used on Apple platforms. During the linking process, linkedit identifies dependencies between object files and libraries, ensuring that all necessary code and data are included in the final output. It plays a crucial role in code signing and dylib (dynamically linked library) management, which are essential for application security and modularity on Apple operating systems. The linker's behavior can be influenced by various command-line flags and linker scripts, allowing developers to fine-tune the linking process for specific needs, such as optimizing executable size or controlling memory layout. Its efficiency and sophisticated handling of complex linking scenarios make it a vital component of the Apple development toolchain.