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

[David Keijser <keijser gmail com>]

2009/2/5 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:
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I have this vague memory of there being a way of marking a function as
a macro in vapi. if not perhaps it should be considered adding it as
macros are quite common.