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Explore if the `C runtime library` is necessary for your C or C+ + program, even if you don't call any standard library functions.
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Understanding C Runtime Libraries: Do You Really Need Them?

When developing in C and C+ + , one of the common questions that arise is: Do I need the C runtime library if my code doesn't call any standard library functions? This inquiry might stem from the frustration of encountering an error message stating that a required library cannot be found when distributing an executable. In this guide, we will explore this question in detail, disentangling the relationship between your code, the C runtime library, and the entry point of your program.

Why the C Runtime Library Matters

Entry Point Requirement

In both C and C+ + , the standard libraries are essential as soon as you define main as the entry point of your program. Here’s what you need to know:

Entry Point: The main function is where the execution of your program begins. Once defined, the presence of certain libraries becomes mandatory, irrespective of whether you utilize their functions.

Implementation Detail: How your program links to these libraries—statically or dynamically—can depend on your operating system and the compilers you choose to use.

For instance, using MSVC on Windows will generally statically link the code necessary for the entry point. Therefore, even with a minimal program containing just:

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You might not need any additional dynamic link library (DLL).

Specific Conditions in C

In the C language, certain functionalities, specifically input/output operations or dynamic memory allocation, rely on the C standard library. Here’s what that implies:

Explicit Dependency: You need to include specific headers from the standard library to utilize its features. If your code never directly or indirectly includes these headers, it won't have any DLL dependencies.

Windows Header Exclusion: For example, using # include <windows.h> does not automatically pull in any headers from the C standard library.

C+ + Specific Considerations

C+ + introduces additional complexities regarding its runtime dependencies:

Dependence on Standard Library: Certain language constructs, particularly for dynamic memory management, require the standard library. For instance:

Operations using new, new[], delete, and delete[] internally depend on the C runtime library.

Direct Usage: Even if you don't use standard include files, merely using these C+ + instructions means you will still need access to the runtime.

Delving into the WinAPI

Windows applications often utilize the Windows API:

Universal Availability: Functions from the WinAPI are available on all Windows systems. If you adhere to using functions that are compatible with older versions of Windows, you'll avoid DLL dependency issues without needing to statically link to the standard library.

Portability: This careful handling of functions ensures your program remains portable across various Windows releases.

Static Linking as an Optimal Solution

Both C and C+ + platforms generally provide options for static linking of the standard library:

Static Linking: This approach bundles the necessary parts of the standard library with your executable, eliminating the need for external dynamic libraries. It’s often the preferred option, particularly unless you are working on GUI applications with C.

Conclusion

In summary, whether you need to include the C runtime library mainly hinges on how you structure your program and the functions you utilize. Always keep in mind:

Using the main function requires certain runtime dependencies.

C programs build dependency strictly via included headers; whereas C+ + may require the runtime for core language features, regardless of headers.

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