Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking

> On Mon, Dec 14, 2015 at 2:37 PM, Stefan Beller <sbeller@google.com> wrote:
>> Provide a wrapper to read(), similar to xread(), that restarts on
>> EINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to
>> handle polling itself, possibly polling multiple sockets or performing
>> some other action.
>>
>> Signed-off-by: Stefan Beller <sbeller@google.com>
>> ---
>> diff --git a/wrapper.c b/wrapper.c
>> @@ -252,6 +252,28 @@ ssize_t xread(int fd, void *buf, size_t len)
>> + * xread_nonblock() is the same a read(), but it automatically restarts read()
>> + * interrupted operations (EINTR). xread_nonblock() DOES NOT GUARANTEE that
>> + * "len" bytes is read. EWOULDBLOCK is turned into EAGAIN.
>
> The last sentence is confusing. From the commit message, we learn that
> this function doesn't care about EAGAIN or EWOULDBLOCK, yet the above
> comment seems to imply that it does. What it really ought to be saying
> is that "as a convenience, errno is transformed from EWOULDBLOCK to
> EAGAIN so that the caller only has to check for EAGAIN".