Re: [Xen-devel] Mini-os fbfront.c unused variable complaint

[John McDermott CIV <john.mcdermott@xxxxxxxxxxxx>]

Ian,

Agreed; this warning is very annoying. The problem is in several files, like a 
design pattern issue. So far it has popped up in fbfront.c, blkfront.c, and 
netfront.c, but the code is nice clean code, so the problem is very regular. We 
are running Fedora 16 and Xen 4.1.2.

----

[mc@xenpro3 ~]$ gcc --version
gcc (GCC) 4.6.2 20111027 (Red Hat 4.6.2-1)
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

----

Here is an example of what I have been doing to get rid of the warning:

----
[mc@xenpro3 xenon]$ hg diff extras/mini-os/fbfront.c
diff -r 8cfe801d065d extras/mini-os/fbfront.c
--- a/extras/mini-os/fbfront.c  Mon Feb 06 08:37:59 2012 -0500
+++ b/extras/mini-os/fbfront.c  Wed Feb 08 09:52:06 2012 -0500
@@ -142,6 +142,9 @@
 abort_transaction:
     free(err);
     err = xenbus_transaction_end(xbt, 1, &retry);
+    if (message) {
+       printk("Abort transaction %s", message);
+    }
     goto error;
 
 done:
@@ -503,6 +506,9 @@
 abort_transaction:
     free(err);
     err = xenbus_transaction_end(xbt, 1, &retry);
+    if (message) {
+       printk("Abort transaction %s", message);
+    }
     goto error;
 
 
 done:
[mc@xenpro3 xenon]$
----

On Feb 8, 2012, at 9:15 AM, Ian Campbell wrote:

> On Mon, 2012-02-06 at 19:05 +0000, John McDermott CIV wrote:
>> Xen Developers,
>> 
>> FWIW, in trying to compile mini-os on Xen 4.1.2, I get a variable set
>> but not used warning for variable 'message' in function init_kbdfront.
>> (Looks like another one just like it, in function init_fbfront, from
>> the same file.) My source won't compile with these warnings. I could
>> not find a patch for this in xen-4.1-testing.hg Xenbits.
> 
> This new, enabled by default, compiler warning is very annoying, even
> though it happens to be correct. Which distro has done it? (or maybe
> it's just new enough gcc which is to blame).
> 
>> It looks like a conditional printk got left out after the label
>> 'abort_transaction'. I don't understand fbfront.c well enough to
>> suggest a patch. Its low priority for me, because I am going to stick
>> some plausible code in there for now.
> 
> I think an unconditional printk including the %s and message is all
> which is required here. If you've got some plausible code you may as
> well post it.
> 
> Thanks,
> Ian.
> 
>> 
>> Sincerely,
>> 
>> John
>> ----
>> What is the formal meaning of the one-line program
>> #include "/dev/tty"
>> 
>> J.P. McDermott                       building 12
>> Code 5542                    john.mcdermott@xxxxxxxxxxxx
>> Naval Research Laboratory    voice: +1 202.404.8301
>> Washington, DC 20375, US     fax:   +1 202.404.7942
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
> 

----
What is the formal meaning of the one-line program
#include "/dev/tty"

J.P. McDermott                  building 12
Code 5542                       john.mcdermott@xxxxxxxxxxxx
Naval Research Laboratory       voice: +1 202.404.8301
Washington, DC 20375, US        fax:   +1 202.404.7942











_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel