Why Use `extern 'C'` When Including C Headers in C ?

Understanding the Need for extern "C" in C to Include C Headers

In the realm of C programming, it is sometimes necessary to include header files written in the C language. However, this presents a challenge as C compilers expect headers to conform to the C Application Binary Interface (ABI). To resolve this mismatch, the extern "C" directive plays a crucial role.

When to Use extern "C"{ #include }

The extern "C" directive is employed when including C headers within a C program. It instructs the compiler to interpret the contents of the included header using the C ABI rather than the C ABI. This allows the linker to generate code compatible with both C and C code segments.

Compiler/Linker Level Explanation

At the compiler level, extern "C" notifies the compiler that the enclosed code block should be treated as C code. This affects the name mangling of functions and structures, ensuring that they adhere to the C ABI. The linker, in turn, can properly resolve symbols and generate executable code that seamlessly integrates C and C components.

Compilation/Linking Impact

By declaring the inclusion of a C header using extern "C", the compiler:

• Generates code using the C ABI, preserving the function and structure names as specified in the header.
• Prevents unexpected symbol resolution errors during linking by instructing the linker to search for symbols in both the C and C code segments.

In summary, extern "C"{ #include } is essential in C programs that incorporate C headers. It ensures that the compiler and linker handle the included code as C code, preventing symbol resolution conflicts and enabling seamless integration of C and C components.

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