Re: [PATCH v5 3/8] convert: Split start_multi_file_filter into two separate functions

On Tue, Apr 11, 2017 at 10:01:02PM +0200, Lars Schneider wrote:

quoted

If you initialize errno to 0 right before a syscall, then yes, you can
trust it without checking the return value of the syscall. I wouldn't
trust it before calling more complicated functions, though. Not even
xwrite(), which may see EINTR and keep going (which is OK for checking
for EPIPE, but not checking generally for errno values).

Should we remove all the errno checks here as we don't have any direct 
"write" etc syscalls anyways then?

Yeah, you should be trusting the return value from the various
sub-functions. Usually you'd check "errno == EPIPE" only when you saw an
error return but you want to _ignore_ EPIPE. This is what
filter_buffer_or_fd() is doing.

But the code here is the opposite case. It definitely wants to treat
EPIPE as an error. But that should be happening already because any
EPIPE we get would come with an error-return from one of the
packet_write() functions.

So I would say that "err || errno == EPIPE" here can just become "err",
and ditto in apply_multi_file_filter().

-Peff