Internals of linking and dynamic linking

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Internals of linking and dynamic linking

Internals of Linking

Linking is the process of combining object files and libraries to create an executable file or a shared library.

Static Linking

In static linking, the linker combines the object files and libraries at compile time, creating a single executable file that contains all the necessary code and data. This executable file can then be distributed and run on other machines without requiring the original source code or libraries.

The steps involved in static linking are:

  • Compilation: Source code is compiled into object files.
  • Linking: Object files and libraries are linked together to create an executable file.

Dynamic Linking

In dynamic linking, the executable file is created without the library code. Instead, the executable file includes a reference to the required libraries. The libraries are loaded into memory at runtime and linked to the executable file. This allows multiple programs to share the same libraries, reducing the amount of memory required to run multiple programs.

The steps involved in dynamic linking are:

  • Compilation: Source code is compiled into object files.
  • Linking: The executable file is created with references to the required libraries.
  • Loading: The operating system loads the required libraries into memory when the executable is run.
  • Linking: The libraries are linked to the executable file at runtime.

Benefits of Linking

Linking provides several benefits:

  • Code reuse: Libraries can be shared by multiple programs, reducing duplication of code.
  • Modularity: Code can be organized into separate libraries, making it easier to maintain and update.
  • Efficiency: Static linking can improve performance by reducing the number of function calls and memory accesses.

Dynamic Linking

Dynamic Linking is a technique used by operating systems to allow multiple programs to share a single copy of a library or code module at runtime. In this technique, the library code is not copied into the program executable, but rather the program executable is linked to the library at runtime.

The advantages of Dynamic Linking include:

  • Reduced executable size: Since the library code is not included in the program executable, the size of the executable is reduced, making it faster to load and execute.
  • Memory savings: Since multiple programs can share a single copy of a library, it saves memory resources, particularly when multiple programs use the same library.
  • Flexibility: Dynamic Linking allows for updates to the library to be made without the need to recompile the program. This makes it easier to fix bugs or add new features to the library.
  • Improved performance: Dynamic Linking can improve performance by reducing the memory footprint of the program, allowing it to run more efficiently.

The process of Dynamic Linking involves several steps, including:

  1. The program executable is loaded into memory.
  2. The linker checks the program for any unresolved symbols, which are references to functions or variables that are defined in the library.
  3. The linker loads the library into memory and resolves the unresolved symbols by linking them to the library functions or variables.
  4. The program is then ready to execute, with the library code available at runtime.

Dynamic Linking is widely used in modern operating systems, including Windows, Linux, and macOS.

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