IPC message queue overflow consequences

Question

I am creating a C application, which will be executed in openwrt router device. Because of limited resources I'm a bit scared about the message queue. What if the "reader" application, which takes the messages from the queue, crash and the "writer" still sends the messages? Should I be worried about the device's memory or will the message queue clean itself eventually?

EDIT I realised that I wasn't clear enough about my task. One application will be sending messages and other will be reading and processing them.

Answer 1

See the documentation for msgsnd :

The queue capacity is governed by the msg_qbytes field in the associated data structure for the message queue. During queue creation this field is initialized to MSGMNB bytes, but this limit can be modified using msgctl(2).

If insufficient space is available in the queue, then the default behavior of msgsnd() is to block until space becomes available. If IPC_NOWAIT is specified in msgflg, then the call instead fails with the error EAGAIN.

So the sender will wait for the receiver to process a message, unless you use IPC_NOWAIT , in which case it returns EAGAIN and the sender can check for this error code.

The default maximum buffer size is specified in a constant called MSGMNB. You can print this value to see what it is on your system. To change the maximum size for your queue, you can use the function msgctl .