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

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. Daniel