Call C libraries

Declare C functions in a .plentyi interface and import it as a module. C’s abs uses int, which is i32 on Plenty’s supported target. The wrapper rejects the minimum integer, which C cannot negate.

Save this as c_math.plentyi:

extern def abs_raw(value: i32) -> i32 = "abs"

pub def absolute(value: i32) -> Option[i32]:
    if value == -2147483648i32:
        return Nothing
    Some(abs_raw(value))

import c_math

def main() -> Result[(), IoError]:
    print(c_math.absolute(-42i32))?
    print(c_math.absolute(-2147483648i32))?
    Ok(())

Option[i32].Some(42)
Option[i32].Nothing

The C standard library is already linked. For another library, pass its archive or driver options explicitly, for example --link-arg /path/to/libexample.a or --link-arg -L/path/to/libs --link-arg -lexample. A shared library also needs to be discoverable by the system loader when the application runs.

The interface author must check the C header and document pointer lifetimes, ownership, and errors. Plenty does not verify the native implementation; application code should use typed wrappers. pub exposes a name to Plenty imports; it does not export a C symbol. See the C interface reference for the supported ABI.