GBool JBIG2Stream::readByte(int *x) {
 int c0;

  if ((c0 = curStr->getChar()) == EOF) {
    return gFalse;
  }
  *x = c0;
  if (c0 & 0x80) {
    *x |= -1 - 0xff;
  }
  return gTrue;
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.