Re: [PATCH] script: evaluate errno only if read() sets it

[Ruediger Meier <sweet_f_a@gmx.de>]

I have a question and a comment about my own patch :)

On Thursday 02 July 2015, Ruediger Meier wrote:

> @@ -367,7 +365,7 @@ static void handle_signal(struct script_control
> *ctl, int fd)
>
>  	bytes = read(fd, &info, sizeof(info));
>  	if (bytes != sizeof(info)) {
> -		if (errno == EAGAIN)
> +		if (bytes < 0 && errno == EAGAIN)
>  			return;

Should we also return on EINTR here like we do in handle_io()?

>  		fail(ctl);
>  	}


And I see some more potential problems. For example see this snippet 
from handle_io();

	bytes = read(fd, buf, sizeof(buf));
	if (bytes < 0) {
		DBG(IO, ul_debug(" read failed"));
		if (errno == EAGAIN || errno == EINTR)
			return;
		fail(ctl);
	}

We are using errno after DBG(). But in theory printf() or whatever we do 
in DBG() could change errno. Wouldn't it be a good idea to write 
generally all DBG macros errno-invariant?

cu,
Rudi