Re: authenc compile warnings in current net-2.6.24

[David Miller <davem@davemloft.net>]

From: Sebastian Siewior <netdev@ml.breakpoint.cc>
Date: Wed, 10 Oct 2007 21:53:37 +0200

> * Oliver Hartkopp | 2007-10-10 19:53:53 [+0200]:
> 
> > CC [M] crypto/authenc.o
> > crypto/authenc.c: In function ?crypto_authenc_hash?:
> > crypto/authenc.c:88: warning: ?cryptlen? may be used uninitialized in this 
> > function
> > crypto/authenc.c:87: warning: ?dst? may be used uninitialized in this 
> > function
> > crypto/authenc.c: In function ?crypto_authenc_decrypt?:
> > crypto/authenc.c:163: warning: ?cryptlen? may be used uninitialized in this 
> > function
> > crypto/authenc.c:163: note: ?cryptlen? was declared here
> > crypto/authenc.c:162: warning: ?src? may be used uninitialized in this 
> > function
> > crypto/authenc.c:162: note: ?src? was declared here
> >
> > do you already know these warnings?
> 
> Those warnings are looking like a compiler bug to me.

It's just not smart enough to see that cryptlen's initialization
and it's use in the auth_unlock label path are both protected
by 'err' being non-zero.

To be honest I don't know of any compiler which commits enough
flow variable analysis to support doing %100 accurate warnings
in situations like this.

Since the compiler is unlikely to do so, I think we should fix
it somehow because useless warnings just distract.