The D programming language is known for its ability to seamlessly integrate with C code. The DMD compiler, which is the reference implementation of the D programming language, provides several extensions that allow developers to take full advantage of C code and libraries. In this article, we will explore some of the DMD C compiler-specific extensions and how they can be useful in D programming.

Interfacing with C code

DMD offers various mechanisms to interface with C code. These extensions make it easier for D developers to work with existing C libraries or leverage platform-specific code. Let’s take a look at some of these extensions.

Linking C libraries

DMD allows you to link C libraries directly. The -L option is used to specify the directory containing the C library, and -l option is used to specify the name of the library.

version(Windows) {
    pragma(lib, "mylib.dll");
} else version(Linux) {
    pragma(lib, "libmylib.so");
}

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C function declarations

DMD provides a way to declare C functions using the extern(C) keyword. This keyword tells the compiler that the function will use C calling conventions. You can also specify the C function name using the @ symbol.

extern(C) int foo(int arg) @ "c_function_name";

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C struct support

DMD also offers support for working with C structs. You can define D structs that directly correspond to C structs using the extern(C) keyword.

extern(C) struct MyCStruct {
    int x;
    float y;
}

MyCStruct myStruct;

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Inline assembly

DMD allows you to include inline assembly code within your D code. This can be useful for performance-critical sections or when you need to access platform-specific features.

inline asm {
    mov eax, 42;
    add eax, ebx;
}

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Conclusion

The DMD C compiler-specific extensions provide powerful tools for interfacing with C code and leveraging platform-specific features within D programs. These extensions enable seamless integration between D and C, making it easier to work with existing C libraries or incorporate low-level operations into D programs. By taking advantage of these extensions, D developers can enjoy the best of both worlds: the modern and expressive features of D, combined with the power and compatibility of C.

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