Re: [PATCH] kernel: Fix ftrace.c compiler warning when callingftrace_nop_replace()

[John Kacur]

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On Mon, 23 May 2011, Steven Rostedt wrote:

> On Sun, 2011-05-22 at 18:36 -0700, H. Peter Anvin wrote:
> > On 05/22/2011 06:19 PM, Eduardo Silva wrote:
> > > the function ftrace_nop_replace() returns a 'static const unsigned char *'
> > > value, so when the caller perform a direct assignment to a
> > > 'static unsigned char *', the compiler raise the following warning message:
> > > 
> > >  ftrace.c:308:6: warning: assignment discards qualifiers from pointer target type
> > >  ftrace.c:318:6: warning: assignment discards qualifiers from pointer target type
> > > 
> > > Adding the proper casts the message goes away.
> > > 
> > > Signed-off-by: Eduardo Silva <edsiper@xxxxxxxxx>
> > 
> > This quiets a warning of something that potentially looks like a real
> > bug.  Perhaps "new" should be const?
> 
> Although there is no real bug here, I hate these "hide the warning"
> patches.
> 
> The real solution is to change all the users into const *. This should
> be doable as the new and old pointers are not modified.
> 
> And remember:
> 
> 	char *changes;
> 	const char *no_changes;
> 
> 	no_changes = changes;  /* is OK! (no compiler warnings) */
> 
> 	changes = no_changes; /* is not OK. (compiler will warn). */
> 
> -- Steve

The following needs some testing, just compile tested for now.