kovidgoyal/kitty · warning

Incomplete signal read from signalfd

Error message

Incomplete signal read from signalfd

What it means

read() from signalfd returned a size that is zero or not a whole multiple of sizeof(struct signalfd_siginfo), which should never happen with a correctly sized buffer; the loop bails for this iteration.

Source

Thrown at kitty/loop-utils.c:155

void
read_signals(int fd, handle_signal_func callback, void *data) {
#ifdef HAS_SIGNAL_FD
    static struct signalfd_siginfo fdsi[32];
    siginfo_t si;
    while (true) {
        ssize_t s = read(fd, &fdsi, sizeof(fdsi));
        if (s < 0) {
            if (errno == EINTR) continue;
            if (errno == EAGAIN) break;
            log_error("Call to read() from read_signals() failed with error: %s", strerror(errno));
            break;
        }
        if (s == 0) break;
        size_t num_signals = s / sizeof(struct signalfd_siginfo);
        if (num_signals == 0 || num_signals * sizeof(struct signalfd_siginfo) != (size_t)s) {
            log_error("Incomplete signal read from signalfd");
            break;
        }
        for (size_t i = 0; i < num_signals; i++) {
            si.si_signo = fdsi[i].ssi_signo;
            si.si_code = fdsi[i].ssi_code;
            si.si_pid = fdsi[i].ssi_pid;
            si.si_uid = fdsi[i].ssi_uid;
            si.si_addr = (void *)(uintptr_t)fdsi[i].ssi_addr;
            si.si_status = fdsi[i].ssi_status;
            si.si_value.sival_int = fdsi[i].ssi_int;
            if (!callback(&si, data)) break;
        }
    }
#else
    static char buf[sizeof(siginfo_t) * 8];
    static size_t buf_pos = 0;
    while (true) {
        ssize_t len = read(fd, buf + buf_pos, sizeof(buf) - buf_pos);

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Rule out kernel/libc oddities (reboot, update system)
2. Upgrade kitty
3. Report upstream with kernel version if reproducible

When it happens

Trigger: Kernel/libc inconsistency or memory corruption producing a partial signalfd_siginfo record.

Common situations: Essentially never observed; would indicate a kernel bug, incompatible libc, or memory corruption.

Related errors

• Call to read() from read_signals() failed with error: %s
• This must be run as kitten choose-files
• Pipe to kitten was broken while sending data to it
• Failed to find cwd of process with pid: {pid}
• Unknown test type: %s

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/faf976e7303589df. Report an issue: GitHub.