C Interop & Translation

One of Chemical's greatest strengths is its perfect relationship with the C programming language.

Calling C from Chemical

You can call any C function by declaring its signature with the @extern attribute.

@extern

public func malloc(size : usize) : *void



@extern

public func free(ptr : *void) : void



public func main() {

    unsafe {

        var p = malloc(1024)

        free(p)

    }

}

C-Compatible Types

When interacting with C, it is recommended to use the types prefixed with c_ or the direct C type names to ensure binary compatibility:

• char, short, int, long, longlong
• uchar, ushort, uint, ulong, ulonglong

C Structs

To use a C struct, mark it as @extern.

@extern

struct CPoint {

    var x : int

    var y : int

}

How C Translation Works

When you build a Chemical project, the compiler performs the following steps:

1. Parsing: Reads your .ch files into an AST.
2. Semantic Analysis: Checks types, visibility, and logic.
3. C Generation: Translates the Chemical AST into highly optimized C99/C11 code.
4. C Compilation: Hand off the generated C code to a back-end like Clang or TCC to produce the final binary.

Benefits of this Approach

• Portability: Chemical code can run anywhere a C compiler exists.
• Performance: You get the optimization benefits of mature C compilers like Clang and GCC.
• Interoperability: Linking with existing C/C++ libraries is as simple as adding them to your build.lab file.

Translating C to Chemical

The Chemical compiler can also perform the reverse! You can use ctx.translate_to_chemical in a build.lab script to automatically generate Chemical signatures from C header files.

// In build.lab

const lib_mod = ctx.c_file_module("", "my_c_lib", "lib.c", [])

ctx.translate_to_chemical(lib_mod, "src/gen/lib_bindings.ch")

Congratulations! You have reached the end of the Chemical documentation. You are now ready to build world-class systems and web applications.