Extern & FFI

Extern Functions

Use extern "C" to declare C functions that can be called from Djinn:

extern "C" {
    i32 printf(i8* format, ...);
    i32 puts(i8* s);
    void* malloc(size_long size);
    void free(void* ptr);
}

These are linked at compile time against the C standard library.

Extern functions are called like regular Djinn functions:

extern "C" {
    i32 printf(i8* format, ...);
}

i32 main() {
    printf("Hello %s! Answer: %d\n", "World", 42);
    return 0;
}

C variadic functions (like printf) are supported with ...:

extern "C" {
    i32 printf(i8* format, ...);
    i32 sprintf(i8* buf, i8* format, ...);
}

C math functions are available through extern declarations:

extern "C" {
    f64 sqrt(f64 x);
    f64 pow(f64 base, f64 exp);
    f32 sqrtf(f32 x);
}

The standard library wraps common extern declarations. Import them directly:

import std::types;
import std::libc;

i32 main() {
    printf("Using std::libc\n");
    return 0;
}

See Built-in Types for the full standard library reference.