tests/ui/c-variadic/roundtrip.rs

//@ run-pass
//@ ignore-backends: gcc
#![feature(c_variadic, const_c_variadic, const_destruct, const_raw_ptr_comparison)]

use std::ffi::*;

// In rustc we implement `va_arg` for the callee reading from a VaList, but still rely on LLVM
// for exactly how to pass c-variadic arguments and for constructing the VaList. Here we test
// that the rustc implementation works with what LLVM gives us.

#[allow(improper_ctypes_definitions)]
const unsafe extern "C" fn variadic<T: VaArgSafe>(mut ap: ...) -> (T, T) {
    let x = ap.next_arg::<T>();
    // Intersperse a small type to test alignment logic. A `u32` (i.e. `c_uint`) is the smallest
    // type that implements `VaArgSafe`: smaller types would automatically be promoted.
    assert!(ap.next_arg::<u32>() == 0xAAAA_AAAA);
    let y = ap.next_arg::<T>();

    (x, y)
}

macro_rules! roundtrip {
    ($ty:ty, $a:expr, $b:expr) => {
        const {
            let a: $ty = $a;
            let b: $ty = $b;
            let (x, y) = variadic::<$ty>(a, 0xAAAA_AAAAu32, b);
            assert!(a == x);
            assert!(b == y);
        }

        let a: $ty = $a;
        let b: $ty = $b;
        assert_eq!(variadic::<$ty>(a, 0xAAAA_AAAAu32, b), (a, b))
    };
}

macro_rules! roundtrip_ptr {
    ($ty:ty, $a:expr, $b:expr) => {
        const {
            let a: $ty = $a;
            let b: $ty = $b;
            let (x, y) = variadic::<$ty>(a, 0xAAAA_AAAAu32, b);
            assert!(a.guaranteed_eq(x).unwrap());
            assert!(b.guaranteed_eq(y).unwrap());
        }

        let a: $ty = $a;
        let b: $ty = $b;
        assert_eq!(variadic::<$ty>(a, 0xAAAA_AAAAu32, b), (a, b))
    };
}

fn main() {
    unsafe {
        roundtrip!(i32, -1, -2);
        roundtrip!(i64, -1, -2);
        roundtrip!(isize, -1, -2);
        roundtrip!(c_int, -1, -2);
        roundtrip!(c_long, -1, -2);
        roundtrip!(c_longlong, -1, -2);

        roundtrip!(u32, 1, 2);
        roundtrip!(u64, 1, 2);
        roundtrip!(usize, 1, 2);
        roundtrip!(c_uint, 1, 2);
        roundtrip!(c_ulong, 1, 2);
        roundtrip!(c_ulonglong, 1, 2);

        roundtrip!(f64, 3.14, 6.28);
        roundtrip!(c_double, 3.14, 6.28);

        static mut A: u32 = 1u32;
        static mut B: u32 = 2u32;
        roundtrip_ptr!(*const u32, &raw const A, &raw const B);
        roundtrip_ptr!(*mut u32, &raw mut A, &raw mut B);
    }
}