Function register

crates/stdlib/src/faulthandler.rs:1119–1167

(args: RegisterArgs, vm: &VirtualMachine)

    #[cfg(unix)]
    #[pyfunction]
    fn register(args: RegisterArgs, vm: &VirtualMachine) -> PyResult<()> {
        check_signum(args.signum, vm)?;

        let fd = get_fd_from_file_opt(args.file, vm)?;

        let signum = args.signum as usize;

        // Get current handler to save as previous
        let previous = if !user_signals::is_enabled(signum) {
            unsafe {
                let mut action: libc::sigaction = core::mem::zeroed();
                action.sa_sigaction = faulthandler_user_signal as *const () as libc::sighandler_t;
                // SA_RESTART by default; SA_NODEFER only when chaining
                // (faulthandler.c:860-864)
                action.sa_flags = if args.chain {
                    libc::SA_NODEFER
                } else {
                    libc::SA_RESTART
                };

                let mut prev: libc::sigaction = core::mem::zeroed();
                if libc::sigaction(args.signum, &action, &mut prev) != 0 {
                    return Err(vm.new_os_error(format!(
                        "Failed to register signal handler for signal {}",
                        args.signum
                    )));
                }
                prev
            }
        } else {
            // Already registered, keep previous handler
            user_signals::get_user_signal(signum)
                .map(|u| u.previous)
                .unwrap_or(unsafe { core::mem::zeroed() })
        };

        user_signals::set_user_signal(
            signum,
            user_signals::UserSignal {
                enabled: true,
                fd,
                all_threads: args.all_threads,
                chain: args.chain,
                previous,
            },
        );

        Ok(())
    }

    #[cfg(unix)]
    #[pyfunction]