childKillPosix

fn childKillPosix(child: *process.Child) !void {
    // Entire function body is intentionally uncancelable.

    const pid = child.id.?;

    while (true) switch (posix.errno(posix.system.kill(pid, .TERM))) {
        .SUCCESS => break,
        .INTR => continue,
        .PERM => return error.PermissionDenied,
        .INVAL => |err| return errnoBug(err),
        .SRCH => |err| return errnoBug(err),
        else => |err| return posix.unexpectedErrno(err),
    };

    if (have_wait4) {
        var status: if (builtin.link_libc) c_int else i32 = undefined;
        while (true) switch (posix.errno(posix.system.wait4(pid, &status, 0, null))) {
            .SUCCESS => return,
            .INTR => continue,
            .CHILD => |err| return errnoBug(err), // Double-free.
            else => |err| return posix.unexpectedErrno(err),
        };
    }

    if (have_waitid) {
        const linux = std.os.linux; // Bypass libc which has the wrong signature.
        var info: linux.siginfo_t = undefined;
        while (true) switch (linux.errno(linux.waitid(.PID, pid, &info, linux.W.EXITED, null))) {
            .SUCCESS => return,
            .INTR => continue,
            .CHILD => |err| return errnoBug(err), // Double-free.
            else => |err| return posix.unexpectedErrno(err),
        };
    }

    var status: if (builtin.link_libc) c_int else i32 = undefined;
    while (true) switch (posix.errno(posix.system.waitpid(pid, &status, 0))) {
        .SUCCESS => return,
        .INTR => continue,
        .CHILD => |err| return errnoBug(err), // Double-free.
        else => |err| return posix.unexpectedErrno(err),
    };
}