Re: [Qemu-devel] [PATCH] osdep: pass const char pointer to setsockopt

[Stefan Hajnoczi <stefanha@gmail.com>]

On Wed, Mar 06, 2013 at 09:07:25PM +0800, Lei Li wrote:
> On 03/06/2013 05:56 PM, Stefan Hajnoczi wrote:
> >On Tue, Mar 05, 2013 at 05:51:21PM +0800, Lei Li wrote:
> >>Pass the right type for setsockopt(), and this will also
> >>fix the compiler warning when cross build for qemu-ga.exe:
> >>
> >>util/osdep.c: In function 'socket_set_nodelay':
> >>util/osdep.c:69:5: warning: passing argument 4 of 'setsockopt' from
> >>                    incompatible pointer type [enabled by default]
> >>In file included from /home/lei/qemu_b/include/sysemu/os-win32.h:30:0,
> >>                  from /home/lei/qemu_b/include/qemu-common.h:46,
> >>                  from util/osdep.c:48:
> >>/usr/i686-w64-mingw32/sys-root/mingw/include/winsock2.h:990:63: note:
> >>                  expected 'const char *' but argument is of type 'int *'
> >>
> >>Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> >>---
> >>  util/osdep.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >>diff --git a/util/osdep.c b/util/osdep.c
> >>index c408261..ce472a9 100644
> >>--- a/util/osdep.c
> >>+++ b/util/osdep.c
> >>@@ -57,7 +57,7 @@ static const char *qemu_version = QEMU_VERSION;
> >>  int socket_set_cork(int fd, int v)
> >>  {
> >>  #if defined(SOL_TCP) && defined(TCP_CORK)
> >>-    return setsockopt(fd, SOL_TCP, TCP_CORK, &v, sizeof(v));
> >>+    return setsockopt(fd, SOL_TCP, TCP_CORK, (char *)&v, sizeof(v));
> >>  #else
> >>      return 0;
> >>  #endif
> >>@@ -66,7 +66,7 @@ int socket_set_cork(int fd, int v)
> >>  int socket_set_nodelay(int fd)
> >>  {
> >>      int v = 1;
> >>-    return setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &v, sizeof(v));
> >>+    return setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, (char *)&v, sizeof(v));
> >Please use qemu_setsockopt() instead of open-coding this.
> >
> >Stefan
> >
> Hi Stefan,
> 
> This compiler warning just shows up without any hacking
> when cross build qemu-ga for windows by:
> 
> ./configure --enable-guest-agent --cross-prefix=i686-w64-mingw32-
> make qemu-ga.exe

I understand you didn't introduce the bug and noticed it when compiling
for Windows.

The correct fix is still to use qemu_setsockopt() which was added in
order to solve this portability problem.

You don't need any casts if you use qemu_setsockopt().

Stefan