Why Use 'extern 'C'{}' When Integrating C Code into C ?

Implications of Integrating C Code in C

When working with C and external C code, it becomes necessary to bridge the gap between their distinct code structures. Integrating C headers within C introduces compatibility challenges due to differences in compilation and linking. This article explores why and how the use of "extern "C"" addresses these issues.

Why Use "extern "C"{ #include }" in C ?

While superficially similar, C and C compilers produce vastly different code. C compilers anticipate C syntax within included header files. However, if a C header is included, the compiler expects it to adhere to C's data formatting, specifically its Application Binary Interface (ABI). This disparity confuses the linker, making it preferable to avoid passing C data to C functions.

Understanding the Compiler/Linker Mismatch

C 's ABI typically alters function and method names. For instance, when attempting to call the "printf()" function without flagging its prototype as a C function, the C compiler generates code that calls "_Zprintf," leading to additional complications.

Resolving the Problem with "extern "C""

To resolve this incompatibility, C headers should be included using "extern "C" {...}". This instructs the compiler to interpret the included code as C, ensuring a match between compiled code formats and preventing linker errors. While some system C headers already consider potential inclusion in C code and apply "extern "C" automatically, this directive is crucial for non-adjusted headers.

The above is the detailed content of Why Use 'extern 'C'{}' When Integrating C Code into C ?. For more information, please follow other related articles on the PHP Chinese website!