Re: [Opencxx-users] parse error on valid code

[Christophe A. <chr...@la...>]

Forward declaration is not necessary with pointer (always a 4-byte unsigned
integer for ia32), but you must use a tag name for the structure to resolve
this lack of information :

typedef struct Link_s {
    struct Link_s *next;
    int value;
} Link;

Anyway, having a typedefed structure without a tag name is something
permissible but bad because we are not sure how each compiler (gcc, vc++,
etc.) would be able to mangle the name of the structure for a parameter in a
global function for example. If someone knows, I would be glad to know it.

Regards.

----- Original Message ----- 
From: "Stefan Seefeld" <se...@sy...>
To: "Shigeru Chiba" <ch...@is...>
Cc: <ope...@li...>
Sent: Tuesday, July 20, 2004 8:10 PM
Subject: Re: [Opencxx-users] parse error on valid code


> Hi Chiba,
>
> thanks for joining in !
>
> Shigeru Chiba wrote:
>
> >>well, but as we just discovered, this doesn't work for C++ in general
where
> >>certain ambiguities have to be resolved using the knowledge about
previously
> >>declared types, variables, etc.
> >
> >
> > Yes, but maintaining the table of type and template names is really
> > complicated.  For example, the parser must be able to recognize Link
> > as a type name in this code snippet:
> >
> > typedef struct {
> >     Link* next;
> >     int value;
> > } Link;
> >
> > (sorry if the syntax above is wrong.  I haven't written C++ code for
> > years. :<)
>
> the syntax is wrong precisely because at the point where a variable of
'Link *'
> is generated nothing is known about 'Link'. The solution is to first issue
a forward
> declaration of 'Link'. And that would indeed solve our problem, too (as
all we
> want to know is that 'Link' is indeed a type, not what kind of type).
>
> I believe that this is true in general for C++: either a type has
previously
> been declared (forward declaration counts), or we have to provide hints
(isn't
> that why the language contains the 'typename' keyword ?)
>
> Kind regards,
> Stefan
>
>
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