The value of SIGCHLD is changed through binding in Linux docker container on MacOS

[sshwy]

Scenario: I'm currently developing my application in a docker container on MacOS. I wish to use kill and other related apis in Rust. Therefore I need to port those signal constants from C header to Rust. However I found that the value of SIGCHLD, which should be 17, is changed to 20.

The bindgen version is 0.65.1.

About the container (generate by Docker Desktop's dev container):

$ uname -a
Linux 64b26c15efbc 6.10.4-linuxkit #1 SMP Mon Aug 12 08:47:01 UTC 2024 aarch64 GNU/Linux
$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux 11 (bullseye)
Release:        11
Codename:       bullseye

Here's a mininal error reproduction (repo):

// main.rs
mod testit {
    #![allow(non_upper_case_globals)]
    #![allow(non_camel_case_types)]
    #![allow(non_snake_case)]
    #![allow(unused)]

    include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
}

fn main() {
    println!("Hello, world!");
    println!(
        "SIGCHLD = {}, but get_sigchld returns {}",
        testit::SIGCHLD,
        unsafe { testit::get_sigchld() }
    );
}

// testit.h
#include <unistd.h>
#include <signal.h>

#ifndef MY_LIB_H
#define MY_LIB_H

int get_sigchld();

#endif

// testit.c
#include "testit.h"

int get_sigchld() { return SIGCHLD; }

Performing cargo run gives the following output:

SIGCHLD = 20, but get_sigchld returns 17

[pvdrz]

my best bet is that bindgen is being fed different system headers than the C compiler you're using to compile testit.c.

I cannot reproduce it on my system:

$ cat input.h
#include <unistd.h>
#include <signal.h>

#ifndef MY_LIB_H
#define MY_LIB_H

int get_sigchld();

#endif
$ bindgen input.h | grep "SIGCHLD"
pub const SIGCHLD: u32 = 17;
$ bindgen --version
bindgen 0.65.1

If I clone and cargo run your repo, I get:

     Running `target/debug/test_bindgen`
Hello, world!
SIGCHLD = 17, but get_sigchld returns 17