dylib function that returns custom type when retrieved produces Segmentation Fault on macOS

[fasihrana]

macOS Sierra: 10.12.6 (16G29)

This issue references the issue created for rust-json

Sample Code is as follows:

Code for the dynamic library function is as follows:

#[macro_use]
extern crate json;

use json::JsonValue;

#[no_mangle]
pub fn methods() -> JsonValue
{
	let rt = array![
		object!{
			"fn" => "method 1"
    		}
	];
	rt
}

Code for my main.rs file is as follows:

extern crate json;
extern crate libloading as lib;

use std::env;
use json::JsonValue;

unsafe fn call_dynamic(libname: &String) -> lib::Result<()> {
	let dylib = try!(lib::Library::new(libname));
	let findmethods: lib::Symbol<fn() -> JsonValue> = dylib.get(b"methods")?;
	let funcs = findmethods();
	println!("{:#}", funcs);
	Ok(())
}

fn main(){
	let args: Vec<String> = env::args().collect();
	unsafe {
		call_dynamic(&args[1]).unwrap();
	}
}

[nagisa]

This could be a duplicate of #5, although I do need a backtrace to make sure.

You should make sure that the functions you’re trying to load dynamically are using a well-known ABI such as the C one. The default does not provide any ABI guarantees. Using a non-fully-repr(C) structures is likely to run into the same problems here.

[fasihrana]

I'm not sure how to generate a backtrace on macOS. Any steps you could link me to?

I had the same problem when I used a custom enum. Then I tried Serde Json with libloading and that works perfectly fine. So my immediate problem has "gone away", but would like to get to the bottom of the issue.

[nagisa]

Run your program under lldb or gdb: lldb program # or gdb program Wait for the program to crash. Then type backtrace And paste the output here. Make sure to compile both your dynamic library and loading program with debug info enabled (i.e. not --release or if rustc is used directly with a -g flag)

…

On Sep 6, 2017 9:06 AM, "fasihrana" ***@***.***> wrote: I'm not sure how to generate a backtrace on macOS. Any steps you could link me to? I had the same problem when I used a custom enum. Then I tried Serde Json with libloading and that works perfectly fine. So my immediate problem has "gone away", but would like to get to the bottom of the issue. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#30 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AApc0gNMlxlym9_6F8rMwoB9_kpUyIQ6ks5sfjZUgaJpZM4PMBYw> .

[nagisa]

Closing as there has been no activity.