Fix mp_hal_stdout_tx_strn(): use ssize_t, loop for partial writes, handle EINTR

[Copilot]

write() returns ssize_t, but the result was stored in int and returned as mp_uint_t, causing silent truncation of large write counts on 64-bit systems. There was also no handling of partial writes or EINTR, meaning stdout output could be silently dropped.

Changes

• bricks/ev3dev/ev3dev_mphal.c
  • Changed ret type from int to ssize_t
  • Added write loop to ensure all bytes are flushed, advancing str pointer on partial writes
  • Retry on EINTR; return bytes written so far on other errors
  • Defensive guard against ret > remaining to prevent unsigned underflow (POSIX-impossible, but explicit)

mp_uint_t mp_hal_stdout_tx_strn(const char *str, size_t len) {
    size_t remaining = len;
    while (remaining > 0) {
        MP_THREAD_GIL_EXIT();
        ssize_t ret = write(STDOUT_FILENO, str, remaining);
        MP_THREAD_GIL_ENTER();
        if (ret < 0) {
            if (errno == EINTR) {
                continue;
            }
            return len - remaining;
        }
        /* Defensive check: POSIX guarantees ret <= remaining, but guard against non-compliant implementations. */
        if ((size_t)ret > remaining) {
            return len;
        }
        str += ret;
        remaining -= (size_t)ret;
    }
    return len;
}

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