Attribute Macro interoptopus_proc::ffi_function

#[ffi_function]

Enable an extern "C" function to appear in generated bindings.

This will derive FunctionInfo for a helper struct of the same name containing the function’s name, parameters and return value.

The following attributes can be provided:

Attribute	Explanation
surrogates(x="y")	Invoke function y to provide a CTypeInfo for parameter x, see below. ⚠️
debug	Print generated helper code in console.
unsafe	Unlocks unsafe options marked: ⚠️

^⚠️ This attribute can lead to undefined behavior when misapplied. When using surrogates you must ensure the surrogate matches the parameter’s type.

Surrogates

When dealing with types outside of your control you will not be able to implement CTypeInfo for them. Instead you need a surrogate, a helper function which returns that info for the type.

The surrogate’s signature is:

fn some_foreign_type() -> CType {
    // Return an appropriate CType
}

Example

use interoptopus::ffi_function;

#[ffi_function]
#[no_mangle]
pub extern "C" fn my_function(x: u32) -> u32 {
    x
}