Re: [RFA/commit] Handle EOF on terminals opened with ENONBLOCK...

[Mark Kettenis <mark.kettenis@xs4all.nl>]

> Date: Thu, 23 Apr 2009 12:14:46 -0700
> From: Joel Brobecker <brobecker@adacore.com>
> 
> What happens is that, by the time GDB makes a read on the pseudo-
> terminal, there is nothing to read yet, and thus gets EOF back.
> The thing to do, to detect our case, is to check the errno value,
> and try again a little later if it's EAGAIN.
> 
> 2009-04-23  Joel Brobecker   <brobecker@adacore.com>
> 
>         * utils.c: Add include of gdb_usleep.h.
>         (defaulted_query): Detect false EOF conditions that happen
>         on terminals opened with the O_NONBLOCK flag when there is
>         nothing to read.
> 
> We've tested this patch on all the hosts that AdaCore supports.
> This includes GNU/Linux, Solaris, AIX, Tru64, MinGW...
> Would it be OK to commit?

Ugh, yuck, this is gross!

I suppose the errno == EAGAIN is supposed to check whether fgetc()
failed.  However, your code has an ferror() in between, which could
clobber errno.  So perhaps it is better to reverse those checks.