The Difference Between Static & Dynamic Libraries Explained

If you’ve ever dabbled in programming or software development, you’ve probably come across terms like DLL, static library, and shared library. These terms can be a bit confusing, especially if you’re new to the field. So, let’s break it down and understand what each of these terms means and how they differ.

What is a DLL?

DLL stands for Dynamic Link Library. It’s a file that contains code and data that multiple programs can use simultaneously. Unlike a static library, a DLL can be dynamically loaded and executed by programs, which means you don’t have to link it at compile-time. It’s linked at run-time instead.

Additional information: You can find a dll file location quite easily when needed by following the provided guide. Also, if you are ever interested in decompiling a DLL file, I’ve got you covered.

DLL: It’s pretty much like a Shared Object, but the cool part is, it doesn’t have to be there when I’m building or even starting the program. I can bring it in later using the special commands (dlopen()/dlsym()) when I actually need it.

Advantages:

• Size: Programs are smaller because they share the library.
• Updates: You can update the library without touching the programs.

Disadvantages:

• Dependencies: Programs might not work if the library is missing or the wrong version.
• Complexity: More potential for things to go wrong at runtime.

Tips and Tricks: If you ever encounter missing DLL files, there are plenty of solutions to fix the problem.

What is a Shared Library?

Shared libraries: They are similar to DLLs but are mainly used in UNIX and UNIX-like operating systems, including Linux. Like a DLL, a shared library is a single file that contains code and data that can be used by multiple programs simultaneously. However, shared libraries are loaded at either load-time or run-time, not just at run-time like DLLs.

Shared Object: This library automatically joins in when I start a program. It’s a separate file that needs to be there when creating the program and running it. I add it to the program using a specific code (like LDOPTS+=-lmylib for a file named mylib.so).

Advantages:

• Efficiency: Multiple programs can use the same library without needing their own copy.
• Updates: Easy to update the library for all programs at once.

Disadvantages:

• Compatibility: Programs might need a specific version of the library.
• Installation: Users need to make sure the library is properly installed.

What is a Static Library?

On the other hand, a static library is a file linked to your program at compile-time. Once linked, all the code and data from the static library become part of your executable file. The main advantage is that you don’t have to worry about distributing additional files. Everything is packed into a single executable.

Static Library: This one actually becomes part of my program when I build it. So, I end up with a bigger, single file with both the program and the library. Just like the Shared Object, I have to include it when I’m creating the program (using code like LDOPTS+=-lmylib for a file named mylib.a).

Advantages:

• Self-Containment: The program’s needs are in one place, making distribution simpler.
• Performance: Sometimes faster, as everything is in one place and no external dependencies exist.

Disadvantages:

• Size: The final program can be quite large, as it includes the library.
• Updates: Updating the library means recompiling the whole program.

Shared Archive: It’s almost identical to a Static Library but has some extra settings. I include it when building the program (using code like LDOPTS+=-lmylibS for a file named mylibS.a). It’s unique because if I want to, I can turn it into a Shared Object or DLL and let other programs use its features.

So, a shared library is like a tool kit that different programs can share and use whenever needed. A static library is a tool kit that becomes a permanent part of one program.

What is the difference between a DLL and a Shared Object?

To make it easy to understand the difference, a DLL is a helper file for programs on Windows computers. A shared object does the same thing but on Linux and UNIX computers. They both let multiple programs use the same features without having separate copies for each program.

Key Differences

1. Portability: DLLs are primarily used in Windows, while shared libraries are used in UNIX systems.
2. Linking Time: Static libraries are linked at compile-time, while DLLs and shared libraries can be linked at run-time.
3. File Size: Programs using static libraries usually have a larger file size because the library becomes part of the executable.
4. Updates: With DLLs and shared libraries, you can update the library file without recompiling all the programs that use it. This is not the case with static libraries.
5. Distribution: You don’t have to distribute any additional files when using static libraries. But with DLLs and shared libraries, you have to ensure that the library file is also distributed or installed on the system where the program will run.

Additional information: If you ever need to delete DLL files, make sure that you do it properly.

So there you have it! We’ve looked at what DLLs, static libraries, and shared libraries are and how they differ. Understanding these differences can help you make better decisions when you’re developing software. Each has its pros and cons, so the choice between them will depend on your specific needs and the platform you’re working on. Hope this clears things up for you!