What happens if STDOUT buffer is overflowed

Question

I wonder what happens if stdout buffer will be overflowed?

For example: app 1 launches the app 2, writes N lines to its stdin and THEN reads its stdout. Second app is just rewrites all it's got from stdin to stdout. At the moment app 1 finishes writing of N lines to app 2 and switches to reading its stdout the app 2 has already finished printing out lines to stdout. And this data is in its stdout's buffer. With increase of N we can overflow buffer.

What happens then? Will app 2 crash or its process blocks? If it's a crash what will be error code (linux)?

EDIT: Some code http://pastebin.com/msMRdxGR
I'm getting SIGPIPE error. (and used wrong labels - app1 is app2 and vice versa).

Sorry for not asking from beginning, but is there a way to avoid this error? If app2 uses 2 threads - one for reading and other for writing. And internal dynamically allocated buffer in heap to exchange data between them. Then I could just suspend writing thread from reading thread if noone reads my stdout. But how can I detect that stdout buf will be soon overflowed?

Answer 1

The process will block if the OS device buffer is full.