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How Can C Code Access C Functionality?

Linda Hamilton
Release: 2024-12-29 01:57:10
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How Can C Code Access C   Functionality?

Bridging the C-C Divide: Exposing C Functionality in C Applications

When working with mixed-language environments, the ability to seamlessly integrate code written in different languages becomes crucial. This problem is even more pronounced when the code is written in C and C , as C 's name mangling poses a challenge.

Consider the need to call C functions from C. In the C domain, the extern "C" keyword allows us to expose functions in a C-compatible manner, providing a straightforward way to use C functions in C applications. However, the reverse scenario, where C code must call C functions, presents a different set of obstacles.

Overcoming Name Mangling

The primary hurdle arises from the name mangling conventions used by C . These conventions make it difficult for C code to directly reference C symbols, leading to unresolved symbol errors.

To overcome this, a common approach involves creating a C API that wraps the C functionality. This API consists of pure C code that exposes the desired functionality without using C classes or objects. By following an object-oriented style, the API can provide a familiar interface for C code to interact with.

Example Implementation

Here's how the C API approach can be implemented in practice:

// *.h file

#ifdef __cplusplus
#define EXTERNC extern "C"
#else
#define EXTERNC
#endif

typedef void* mylibrary_mytype_t;

EXTERNC mylibrary_mytype_t mylibrary_mytype_init();
EXTERNC void mylibrary_mytype_destroy(mylibrary_mytype_t mytype);
EXTERNC void mylibrary_mytype_doit(mylibrary_mytype_t self, int param);

#undef EXTERNC
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// *.cpp file

mylibrary_mytype_t mylibrary_mytype_init() {
  return new MyType;
}

void mylibrary_mytype_destroy(mylibrary_mytype_t untyped_ptr) {
   MyType* typed_ptr = static_cast<MyType*>(untyped_ptr);
   delete typed_ptr;
}

void mylibrary_mytype_doit(mylibrary_mytype_t untyped_self, int param) {
   MyType* typed_self = static_cast<MyType*>(untyped_self);
   typed_self->doIt(param);
}
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In this example, the C API provides a set of functions to create, destroy, and manipulate an object of type MyType, hiding the implementation details of the C classes and objects behind the scenes.

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