Date: Sun, 12 Sep 2004 20:40:24 GMT From: Alfred Perlstein <alfred@freebsd.org> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/71628: [PATCH] cleanup of the usr.sbin/rpcbind code Message-ID: <200409122040.i8CKeOmL029328@freefall.freebsd.org>
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The following reply was made to PR bin/71628; it has been noted by GNATS.
From: Alfred Perlstein <alfred@freebsd.org>
To: Giorgos Keramidas <keramida@freebsd.org>
Cc: Dan Lukes <dan@obluda.cz>, bug-followup@freebsd.org
Subject: Re: bin/71628: [PATCH] cleanup of the usr.sbin/rpcbind code
Date: Sun, 12 Sep 2004 13:35:50 -0700
I'm having a hard time seeing these warnings, how are they
being triggered?
* Giorgos Keramidas <keramida@freebsd.org> [040912 13:07] wrote:
> On 2004-09-12 04:38, Dan Lukes <dan@obluda.cz> wrote:
> > static int
> > init_transport(struct netconfig *nconf)
> > {
> > - int fd;
> > + int fd = fd; /* init to suppres "may be used uninitialized" warning */
>
> Err, no please. GCC complains that fd "may be used uninitialized" because
> of this construct near line 275 and the rest of the function body:
>
> 275 if (nconf->nc_semantics != NC_TPI_CLTS) {
> 276 if ((fd = __rpc_nconf2fd(nconf)) < 0) {
> 277 int non_fatal = 0;
> ...
> 283 return (1);
> 284 }
> ...
> 311 if (nconf->nc_semantics == NC_TPI_CLTS) {
> ...
> 334 while (nhostsbak > 0) {
> ...
> 339 if ((fd = __rpc_nconf2fd(nconf)) < 0) {
> ...
> 452 } else {
> ...
> 466 if (bind(fd, sa, addrlen) < 0) {
>
> Pay attention to this last line. GCC believes that fd can be used
> uninitialized because if NC_TPI_CLTS is not used the bind() call will
> receive an uninitialized value of `fd'. I'm not acquainted with the
> internals of rpcbind() at all, but I know that Alfred Perlstein is.
> He's probably the best person to suggest a fix for this warning, if one
> is really needed.
>
> > struct t_bind taddr;
> > struct addrinfo hints, *res = NULL;
> > struct __rpc_sockinfo si;
> > - SVCXPRT *my_xprt;
> > ! SVCXPRT *my_xprt = my_xprt; /* init to suppres "may be used uninitialized" warning */
>
> No. I don't know why you think that this is a good fix for all the
> uninitialized pointer warnings. It's not. Never :-/
>
> This warning is probably caused by GCC's inability to make sure that when
> `bar' is a pointer this construct is perfectly fine:
>
> if (foo) {
> ...
> if (bar = baz())
> ...
> } else {
> ...
> if (bar = baz2())
> ...
> }
>
> if (blah(bar))
> ...
>
> After a quick glance at the source of rpcbind() I think that there's no way
> that my_xrpt can be used uninitialized. A proper fix for this warning
> would be then to just set my_xrpt to NULL at first and let the rest of the
> function unchanged regarding my_xrpt.
--
- Alfred Perlstein
- Research Engineering Development Inc.
- email: bright@mu.org cell: 408-480-4684
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