Re: [PATCH] GnuTLS support on Woe32

[Eli Zaretskii <eliz@gnu.org>]

> From: claudio.bley@gmail.com (Claudio Bley)
> Date: Wed, 09 Mar 2011 22:12:33 +0100
> 
> > > > +static int
> > > > +wsaerror_to_errno(int err)
> > > > +{
> > > > +  switch (err)
> > > > +    {
> > > > +    case WSAEWOULDBLOCK:
> > > > +      return EAGAIN;
> > > > +    case WSAEINTR:
> > > > +      return EINTR;
> > > > +    default:
> > > > +      return err;
> > > > +    }
> > > > +}
> > > 
> > > Why is this function needed?  Can you extend w32.c:set_errno instead
> > > (if it doesn't already support all the values of WSA* errors that you
> > > need)?
> > 
> > Yes, I could extend w32.c:set_errno, if I move the Windows-specific
> > function to w32.c proper...
> 
> I just had a look at this again. It's not so easy.
> 
> For GnuTLS, I have to map WSAEWOULDBLOCK to EAGAIN. This is set in
> stone.

Set in stone where?  I see this in gnutls.c:

  int
  emacs_gnutls_write (int fildes, struct Lisp_Process *proc, char *buf,
		      unsigned int nbyte)
  {
    register int rtnval, bytes_written;
    gnutls_session_t state = proc->gnutls_state;

    if (proc->gnutls_initstage != GNUTLS_STAGE_READY) {
  #ifdef EWOULDBLOCK
      errno = EWOULDBLOCK;
  #endif
  #ifdef EAGAIN
      errno = EAGAIN;
  #endif
      return -1;
    }

So it looks like it already is prepared to deal with EWOULDBLOCK if
EAGAIN is not available.

> Doing this in w32.c:set_errno would break a lot of other stuff that
> checks for EWOULDBLOCK because that happens to be #define'd to
> WSAEWOULDBLOCK in sys/socket.h:129 (which seems reasonable after all).

If all you need is to produce EAGAIN when you have EWOULDBLOCK (the
other mapping is already in set_errno), it hardly justifies a
function.

But I would like to understand better why you must produce EAGAIN in
the first place.

> It works alright when EWOULDBLOCK is #define'd to EAGAIN. In the end
> it doesn't matter what EWOULDBLOCK is defined to because on Windows
> MinGWs GCC doesn't define it at all, MSVC has it, but WinSock uses
> it's own error codes anyway.

Sorry, I don't follow.  What were you trying to say or suggest here?

> > > > +static ssize_t
> > > > +emacs_gnutls_pull(gnutls_transport_ptr_t p, void* buf, size_t sz)
> > > 
> > > Can we move the Windows-specific functions to w32.c, and only call
> > > them from gnutls.c?  I think we want to keep the Windows-related code
> > > outside w32*.c to the bare minimum.
> > 
> > OK.
> 
> Maybe the GnuTLS specific stuff should also be kept to the bare
> minimum outside of gnutls.c?

What stuff did you have in mind?

> Considering that these functions would have to be non-static in this
> case to be accessible by gnutls.c.

Sure, but I see no problem with that.