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Re: [Qemu-devel] [PATCH] Win32: Don't remove const attribute in type cas
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] [PATCH] Win32: Don't remove const attribute in type casts. |
Date: |
Sat, 13 Jun 2009 17:30:32 +0100 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Stefan Weil wrote:
> Type casts removing the const attribute are bad because
> they hide the fact that the argument remains const.
>
> They also result in a compiler warning (at least with MS-C).
> - return sendto(s->fd, (void *)buf, size, 0,
> + return sendto(s->fd, (const void *)buf, size, 0,
> (struct sockaddr *)&s->dgram_dst, sizeof(s->dgram_dst));
1. Why isn't the (struct sockaddr *) const too?
It is declared like this in at least one Win32 header file:
WINSOCK_API_LINKAGE int PASCAL sendto(SOCKET, const char*,
int, int,
const struct sockaddr*, int);
So why does the buffer pointer need to be const, but the sockaddr
does not, for MS-C to be happy?
2. Possibly just a historical note. Passing a const pointer will
produce compiler warnings or even errors on any platform where
sendto is declared in system headers without const pointer
arguments. I think some old unixes did that, but probably QEMU
isn't targetting any of them.
However, it might be why the (void *) cast was put there in the
first place, as there is no need for any cast at all on platforms
where sendto() is declared the modern way.
3. See 2 - maybe just get rid of the cast?
-- Jamie