devxlogo

extern “C” linkage declaration

extern “C” linkage declaration

It is not uncommon for C++ code fragments to be called by non-C++ programs such as a C-based communication software, COBOL based TP monitors and the likes. However, global functions in C++ cannot be called by non-C++ programs since the function name is very different from the one supplied by the programmer. Why is this? By default, the C++ compiler uses a technique termed name mangling which incorporates the function name with its signature (list of arguments) in order to create a unique name for it, even in case of overloading (this technique is used both for external function and class member functions).

//the following global functions have distinct names generated by the compiler void f(int); //x__f_i this may be the name generated by the compiler for this f()void f(long, char* ); //x__f_pc this may be the name generated by the compiler for this f()

In order to enforce the compiler to avoid name mangling, a global function has to be declared as extern “C”:

extern “C” void f(int); //now the generated name is identical to the one given by the programmer: f

Mind, however, that a function declared as extern “C” cannot be overloaded, and that extern “C” declaration can only be applied to global functions.

See also  5 Benefits of Using Time Tracking Software
devxblackblue

About Our Editorial Process

At DevX, we’re dedicated to tech entrepreneurship. Our team closely follows industry shifts, new products, AI breakthroughs, technology trends, and funding announcements. Articles undergo thorough editing to ensure accuracy and clarity, reflecting DevX’s style and supporting entrepreneurs in the tech sphere.

See our full editorial policy.

About Our Journalist