Playdate crashes if bitmap is sent over serial too quickly

SDK Bug Reports
1

I was doing some experimentation with the serial API and I found that if you send bitmap too quickly the Playdate crashes.

You can use this C program to reproduce (if you're on a posix based system):

#define _DEFAULT_SOURCE
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
  if (argc < 2) {
    printf("No port was given.\n");
    return 1;
  }
  const char *portname = argv[1];

  int fd = open(portname, O_RDWR | O_NOCTTY);
  if (fd == -1) {
    perror("Error opening serial port");
    return 1;
  }

  struct termios tty;
  memset(&tty, 0, sizeof tty);
  if (tcgetattr(fd, &tty) != 0) {
    perror("Error getting terminal attributes");
    close(fd);
    return 1;
  }

  cfsetospeed(&tty, B115200);
  cfsetispeed(&tty, B115200);

  tty.c_cflag &= ~PARENB;
  tty.c_cflag &= ~CSTOPB;
  tty.c_cflag &= ~CSIZE;
  tty.c_cflag |= CS8;
  tty.c_cflag &= ~CRTSCTS;
  tty.c_cflag |= CREAD | CLOCAL;
  tty.c_lflag &= ~ICANON;
  tty.c_lflag &= ~ECHO;
  tty.c_lflag &= ~ECHOE;
  tty.c_lflag &= ~ECHONL;
  tty.c_lflag &= ~ISIG;
  tty.c_iflag &= ~(IXON | IXOFF | IXANY);
  tty.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL);
  tty.c_oflag |= OPOST;
  tty.c_oflag |= ONLCR;

  if (tcsetattr(fd, TCSANOW, &tty) != 0) {
    perror("Error setting terminal attributes");
    close(fd);
    return 1;
  }

  unsigned int t = 0;
  while (1) {
    char msg[12007] = "bitmap\n";
    for (int i = t; i < t + 500; i++)
      msg[i + 7] = 0b11111111;
    int n = write(fd, msg, 12007);

    if (n < 0) {
      perror("Error writing to serial port");
      close(fd);
      return 1;
    }

    t += 1;
    if (t > 11000) t = 0;
  }

  close(fd);
  return 0;
}