Linker

A 'linker' is a crucial software utility that takes multiple object files (containing compiled code and data) and combines them into a single executable file, library, or other loadable module. It resolves references between these object files, ensuring that functions and variables called in one file can access their definitions in another. The linker also handles memory allocation and address assignment, creating the final program image ready for execution. This process is fundamental to the modularity and organization of software development, allowing complex programs to be built from independent components.

Linker meaning with examples

• The C compiler generates object files, which are then passed to the linker. The linker's primary task is to integrate various code sections and data from separate object files. After this linking step, a single executable file is made. This is then suitable for execution on your system, allowing a program to work as expected after compilation. The linker is vital to compilation.
• When developing a large application, source code will often be split across various files. Each file can be compiled to produce an object file. The linker then takes these object files and resolves all the external references to link the different parts of the application into a single, functioning whole. This is a typical workflow when creating software.
• If a library function is used in a program but not defined within the program itself, the linker resolves this by linking the program with the appropriate library. The linker finds the library function's compiled code, which has already been built as a .lib or .so file, and incorporates it into the executable. Without a linker, libraries would be impossible.
• Modern IDEs typically automate the linking process. After compiling source code, the linker is invoked automatically to create the executable. The developer often isn't aware of these details of object files. This integration simplifies software development, but understanding the role of the linker can improve debugging and optimization.