FFI by-value struct function argument error on Windows

[SiegeLord]

This is somewhat complicated and requires an intermediate crate. There is no error (as far as this test can tell) if the intermediate crate is removed. Take these 3 files:

bug.c

#include <stdio.h>

typedef struct
{
    float a, b, c, d;
} S;

void test(S a)
{
    printf("%f %f %f %f\n", a.a, a.b, a.c, a.d);
}

bug.rs

#![crate_id="bug"]
#![crate_type="lib"]

pub struct S
{
    pub a: f32,
    pub b: f32,
    pub c: f32,
    pub d: f32,
}

#[link(name = "bug")]
extern "C"
{
    pub fn test(b: S);
}

test.rs

extern crate bug;

use bug::{test, S};

fn main()
{
    unsafe
    {
        let s1 = S{a: 1.0, b: 2.0, c: 3.0, d: 4.0};
        test(s1);
    }
}

Compile it all together and run test.exe:

gcc -shared bug.c -olibbug.dll
rustc bug.rs
rustc test.rs -L.
test

The output I get is:

0.000000 0.000000 1.000000 2.000000

Expected output:

1.000000 2.000000 3.000000 4.000000

GCC version:

gcc (rev5, Built by MinGW-W64 project) 4.8.1

[klutzy]

Test code works now! Seems to be fixed by #14191

[thestinger]

Closing since that PR added a test.