Subject: Re: [PATCH -next] nfs: fix ISO C90 warning

From: Trond Myklebust <[email-masked]>
Date: Wed, 16 Dec 2009 18:01:37 -0500

On Wed, 2009-12-16 at 23:58 +0100, Thomas Gleixner wrote: 
> On Wed, 16 Dec 2009, Randy Dunlap wrote:
> > On Wed, 16 Dec 2009 17:40:19 -0500 Trond Myklebust wrote:
> > 
> > > On Wed, 2009-12-16 at 14:23 -0800, Randy Dunlap wrote: 
> > > > From: Randy Dunlap <[email-masked]>
> > > > 
> > > > Fix gcc ISO C90 warning:
> > > > 
> > > > fs/nfs/callback.c:356: warning: ISO C90 forbids mixed declarations and code
> > > > 
> > > > Signed-off-by: Randy Dunlap <[email-masked]>
> > > > ---
> > > >  fs/nfs/callback.c |    2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > --- linux-next-20091215.orig/fs/nfs/callback.c
> > > > +++ linux-next-20091215/fs/nfs/callback.c
> > > > @@ -352,8 +352,8 @@ static int check_gss_callback_principal(
> > > >  static int nfs_callback_authenticate(struct svc_rqst *rqstp)
> > > >  {
> > > >  	struct nfs_client *clp;
> > > > -	RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
> > > >  	int ret = SVC_OK;
> > > > +	RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
> > > >  
> > > 
> > > What version of gcc is giving rise to this warning?
> > 
> > > gcc --version
> > gcc (GCC) 4.2.1 (SUSE Linux)
> > 
> > > RPC_IFDEBUG is a macro that either evaluates to its argument, or to
> > > nothing, depending on whether or not RPC_DEBUG is defined or not. In
> > > neither case should it evaluate to anything illegal under C90 rules
> > > afaics.
> > 
> > Yep.  Odd warning.
> 
> Not really. If the debug macro evaluates to nothing then you have:
> 
>     struct nfs_client *clp;
>     ;
>     int ret = SVC_OK;
> 
> So you have a stray semicolon, which is interpreted as an empty code
> line. That qualifies for the mixed declaration and code case :)
> 
> I know it's nitpicking, but ...

Ah... I see what you mean.

So really what we should do is just move that semicolon inside the
macro. That would change the !RPC_DEBUG case to

    struct nfs_client *clp;

    int ret = SVC_OK;

which is 100% legal...

Cheers
  Trond