From: erik quanstrom <quanstro@quanstro.net>
To: 9fans@9fans.net
Subject: Re: [9fans] C compiler question
Date: Sun, 12 Jul 2009 12:59:19 -0400 [thread overview]
Message-ID: <37a4205e0ebcee3f0fd82131999a1e5d@quanstro.net> (raw)
In-Reply-To: <4A595F8D.1080408@tecmav.com>
> 8c silently accept the above definition and sizeof(U) is 100. ???
> The sources which include the definition of "NeverDefined" are
> regularly compiled too and sizeof(U) = 100 + sizeof(NeverDefined).
>
i think the issue is that there isn't currently a distinction
between this
typedef struct A A;
struct A {
int expand[0];
};
which is perfectly legal and this
typedef struct U U;
typedef struct A A;
struct A {
U;
};
which might be allowed, but i can't find any references
that say it is. the argument for having expandable
structures would be it would allow something like this
typedef struct Priv Priv;
typedef struct Pub Pub;
struct Pub {
...
Priv;
};
#pragma incomplete Pub
Pub *pubfn(void);
but i don't see any such uses in /sys/include.
this change will generate a diagnostic for your code,
but be careful. this is a corner of c, and what seems
intuitively correct in the corners can often be wrong.
- erik
; diff -c dcl.c `{yesterday -n2 dcl.c}
dcl.c:541,547 - /n/dump/2009/0710/sys/src/cmd/cc/dcl.c:541,547
l->offset = o;
} else {
if(l->width <= 0)
- if(l->down != T || l->width < 0)
+ if(l->down != T)
if(l->sym)
diag(Z, "incomplete structure element: %s",
l->sym->name);
next prev parent reply other threads:[~2009-07-12 16:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-12 3:59 Adriano Verardo
2009-07-12 16:59 ` erik quanstrom [this message]
2009-07-14 2:58 ` Adriano Verardo
2009-07-14 3:14 ` erik quanstrom
2009-07-14 14:00 ` Adriano Verardo
2009-07-14 14:57 ` erik quanstrom
2009-07-14 16:26 ` Adriano Verardo
2009-07-14 16:38 ` erik quanstrom
2009-07-14 17:18 ` Roman V Shaposhnik
2009-07-14 17:46 ` erik quanstrom
2009-07-14 18:59 ` Roman V Shaposhnik
2009-07-14 19:29 ` erik quanstrom
2009-07-14 19:45 ` Russ Cox
2009-07-15 11:34 ` Ethan Grammatikidis
2009-07-15 11:38 ` erik quanstrom
2009-07-14 20:28 ` [9fans] pointers to incomplete types Roman V Shaposhnik
2009-07-15 9:25 ` [9fans] C compiler question robert wilson
2009-07-14 4:00 ` Russ Cox
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