linux-kernel - Re: [PATCH] trace, RAS: remove unnecessary const

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Date:	Thu, 19 Mar 2015 11:33:30 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Xie XiuQi <xiexiuqi@...wei.com>
Cc:	akpm@...ux-foundation.org, n-horiguchi@...jp.nec.com,
	rostedt@...dmis.org, gong.chen@...ux.intel.com,
	bhelgaas@...gle.com, tony.luck@...el.com,
	linux-kernel@...r.kernel.org, jingle.chen@...wei.com
Subject: Re: [PATCH] trace, RAS: remove unnecessary const

On Thu, Mar 19, 2015 at 04:50:04PM +0800, Xie XiuQi wrote:
> These parameters are passed by value. There's no need to make them const.

I can think of a reason:

include/trace/../../include/ras/ras_event.h: In function ‘ftrace_raw_event_mc_event’:
include/trace/../../include/ras/ras_event.h:136:35: error: assignment of read-only parameter ‘top_layer’
   __entry->top_layer  = top_layer = 12;
                                   ^
---
diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h
index 79abb9c71772..e4721eac3e25 100644
--- a/include/ras/ras_event.h
+++ b/include/ras/ras_event.h
@@ -133,7 +133,7 @@ TRACE_EVENT(mc_event,
                __assign_str(label, label);
                __entry->error_count            = error_count;
                __entry->mc_index               = mc_index;
-               __entry->top_layer              = top_layer;
+               __entry->top_layer              = top_layer = 12;
                __entry->middle_layer           = mid_layer;
                __entry->lower_layer            = low_layer;
                __entry->address                = address;
---

I'm not saying it is a particularly sane reason and no one would even
*think* of changing TP parameters passed on from higher layers in the TP
itself but I've seen people do lotsa crazy things - things they normally
would never do - so if it doesn't hurt having the const here, what's the
downside of having the compiler do that sanity checking for us too?

Steve, this is an invitation for your crazy fantasy! :-P

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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