Re: [Vala] How to wrap select(2)'s fd_set?

["Michael 'Mickey' Lauer" <mickey vanille-media de>]

Am Friday 30 January 2009 14:26:51 schrieb Michael 'Mickey' Lauer:
> Am Friday 30 January 2009 08:30:43 schrieb Jürg Billeter:
> > FdSet should be a struct, not a class, we do not need reference type
> > semantics here. This eliminates unnecessary heap allocation. FD_ZERO
> > should be bound as initialization method as it just zeroes the streuct.
>
> Understood.
>
> > [CCode (cname = "fd_set", cheader_filename = "sys/select.h"]
> > public struct FdSet {
> >     [CCode (cname = "FD_ZERO")]
> >     public FdSet ();
> >     ...
> > }
>
> With this change, I get a strange C-compilation error:
>
> /local/pkg/fso/fso-gsm0710muxd/src/multiplexer.c: In
> Funktion »multiplexer_writefd«:
> /local/pkg/fso/fso-gsm0710muxd/src/multiplexer.c:324: Fehler: expected
> expression before »do«
> /local/pkg/fso/fso-gsm0710muxd/src/multiplexer.c:325: Fehler: expected
> expression before »do«
> /local/pkg/fso/fso-gsm0710muxd/src/multiplexer.c:326: Fehler: expected
> expression before »do«
>
> The respective generated code is:
>
> gboolean multiplexer_writefd (Multiplexer* self, const char* command, gint
> fd) {
>         fd_set _tmp0 = {0};
>         fd_set readfds;
>         fd_set _tmp1 = {0};
>         fd_set writefds;
>         fd_set _tmp2 = {0};
>         fd_set exceptfds;
>         struct timeval t = {(glong) 1, (glong) 0};
>         gint r;
>         gboolean _tmp3;
>         gssize bwritten;
>         g_return_val_if_fail (self != NULL, FALSE);
>         g_return_val_if_fail (command != NULL, FALSE);
>         readfds = (FD_ZERO (&_tmp0), _tmp0);
>         writefds = (FD_ZERO (&_tmp1), _tmp1);
>         exceptfds = (FD_ZERO (&_tmp2), _tmp2);
>         FD_SET (fd, &writefds);
> ...
>
> I have no idea where this 'do' comes from.

Ok, I now found out:

FD_ZERO is defined as __FD_ZERO which in turn is defined as:

/* We don't use `memset' because this would require a prototype and
   the array isn't too big.  */
#define __FD_ZERO(s) \
  do { \
    unsigned int __i; \
    fd_set *__arr = (s); \
    for (__i = 0; __i < sizeof (fd_set) / sizeof (__fd_mask); ++__i) \
      __FDS_BITS (__arr)[__i] = 0; \
  } while (0)

The valac-generated part

> readfds = (FD_ZERO (&_tmp0), _tmp0);

is a syntax error then.

Anything we can do about that or just give in and leaving FdSet a full class?

-- 
:M: