Daniel Berger
2/14/2007 3:02:00 PM
On Feb 13, 7:17 pm, "George Ogata" <george.og...@gmail.com> wrote:
> On 2/14/07, Daniel Berger <djber...@gmail.com> wrote:
>
> > Hi,
>
> > Ruby 1.8.5 p12
>
> > It looks like there was a prototype change in rb_cvar_set() at some
> > point in the 1.8.x branch. It now takes a 4th parameter (an int). What
> > is the 4th parameter supposed to be?
>
> Hi Dan,
>
> If you poke your nose into the rb_cvar_set() function, you'll see it's
> just a warning enabler flag. Specifically, if this argument is
> nonzero, then in verbose mode (-v, -w) you'll get a warning if you
> modify a class variable from a subclass. As in:
>
> $ ruby -w -e 'class B; @@x = 1; end; class D < B; @@x = 5; end'
> -e:1: warning: already initialized class variable @@x
>
> The flag appears to be used to distinguish between cases such as:
>
> class B
> @@x = 1
> end
>
> class D < B
> @@x = 2 # warning
>
> def f
> @@x = 3 # no warning
> end
>
> def self.f
> @@x = 4 # no warning
> end
> end
>
> Here, although the last 3 assignments to @@x all modify B's @@x, the
> ones inside a def are considered "assignment-style", whereas the "@@x
> = 2" is "declaration-style". Only the latter generates a warning.
Ah, thanks George. It looks like you're supposed to test for the
RB_CVAR_SET_4ARGS macro to stay backwards compatible, too.
Dan