Meeting a terrible fate when calling debug! macro from C

[martinraison]

I have a C program using a rust library that calls the debug! macro. Here is the setup:

system: OS X Mavericks 10.9.4

bar.rs

#![feature(phase)]

#[phase(plugin, link)]
extern crate log;

#[no_mangle]
pub unsafe extern "C" fn test() {
    debug!("Hello");
}

bar.h

void test();

test.c

#include "bar.h"

int main(int argc, char *argv[]) {
    test();
}

I'm able to compile it using

rustc --crate-type staticlib bar.rs
gcc -Wall -o test test.c -L. -lbar

but it crashes at runtime:

$ ./test

You've met with a terrible fate, haven't you?

fatal runtime error:  assertion failed: queue != 0
[1]    42775 illegal hardware instruction  ./test

I don't think the problem is specific to the debug! macro, because I've seen the exact same error in other situations. However this is the simplest example I've found. Note that I've been able to run other C programs using Rust libraries successfully (for example if I replace debug! with println! in the example, then everything is fine).

Maybe I'm missing a step somewhere, but it looks like a bug to me.

[martinraison]

Investigating a bit more, it looks like the assertion queue != 0 fails in at_exit_impl.rs because the queue has not been initialized. So I solved my problem by manually initializing the runtime:

std::rt::init(0, std::ptr::null());

Of course it makes sense now, but is this is the recommended way to do it? It also means many rust libraries will require some kind of init() function to be called (which is fine, I guess).

[kmcallister]

As I see it, the solution is to compile with #![no_std] and provide your own begin_unwind.

[martinraison]

I see - thanks for your reply! I tried using #![no_std] originally but my project is using things like ChanReader which don't seem to be available outside of std.

[thestinger]

You need to use #![no_std] if you want to provide a Rust library with a normal C API. You're running into explicitly undefined behaviour if you aren't initializing the runtime on every thread before using libstd.