Re: [libvirt] [PATCH] safe{read, write}: Don't lie on nonblocking FD

On 16.01.2013 19:31, Daniel P. Berrange wrote: > On Wed, Jan 16, 2013 at 07:27:46PM +0100, Michal Privoznik wrote: >> Currently, whenever somebody calls saferead() on nonblocking FD >> (safewrite() is totally interchangeable for purpose of this >> message) he might get wrong return value. For instance, in the >> first iteration some data is read. The number of bytes read is >> stored into local variable 'nread'. However, in next iterations >> we can get -1 from read() with errno == EAGAIN, in which case the >> -1 is returned despite fact some data has already been read. So >> the caller gets confused. >> >> Moreover, the comment just above the functions says, they act >> like regular read() with nicer handling of EINTR. Well, they >> don't now. > > I think that it is correct that these APIs return -1 on EAGAIN. > These APIs should *not* be used on non-blocking FDs. > In that case I think we have to note it explicitly in the comments.