Static vs. Dynamic Linking: What's the Difference and Which Should I Use?

Static linking and dynamic linking: in-depth analysis and application guide

In the field of software development, "static linking" and "dynamic linking" are key concepts in understanding how code is converted into an executable program.

What is a link?

Linking is the process of combining multiple object modules (created during compilation) into a single executable program. Linking is necessary since code written in languages ​​like C, C++, and C# is often separated into separate source code files.

Static link

Static linking embeds the entire contents of the linked file directly into the executable file. This means that all the code needed by the program is present in the executable file itself.

Dynamic link

In contrast, dynamic linking contains a reference (such as a file name) to an external file within the executable. These external files are called dynamic link libraries (DLLs) or shared libraries and are loaded and executed only when the program is running.

Comparison of advantages and disadvantages

Static link:

• Advantages:
  • Program starts faster because all necessary code is already loaded.
  • Does not depend on external libraries.
• Disadvantages:
  • Executable file size is larger.
  • Changes to statically linked code require recompiling the entire program.

Dynamic link:

• Advantages:
  • Executable file size smaller.
  • Updating and fixing bugs is easier since only dynamic libraries need to be replaced.
• Disadvantages:
  • A runtime error may occur due to version mismatch.
  • "DLL Hell" can result when multiple programs depend on different versions of the same library.

Practical examples of static linking and dynamic linking

For better understanding, consider the following scenario:

Static link:

• main.c contains the main code.
• crtimp.c contains the C runtime library (providing functions such as printf).

During the linking process, main.o and crtimp.o are merged into a single executable file (main). This means that main does not require other libraries to run.

Dynamic link:

• main.c contains the main code.
• crtdll.dll contains the C runtime library.

During the linking process, main.o is merged with crtimp.o (an import library that declares but does not define runtime functions). When main is run, the operating system dynamically links it to crtdll.dll, allowing the program to access runtime functionality without embedding the code in the executable file.

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