hw/remote/mpqemu-link.c:221: bad error checking ? hw/remote/mpqemu-link.c:221:36: warning: logical ‘and’ of mutually exclusive tests is always false [-Wlogical-op] Source code is if (msg->cmd >= MPQEMU_CMD_MAX && msg->cmd < 0) { return false; } Maybe better code: if (msg->cmd >= MPQEMU_CMD_MAX || msg->cmd < 0) { return false; } It might be useful to switch on gcc compiler flag -Wlogical-op to see these warnings.