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Date: Mon, 27 Aug 2007 13:41:31 -0700 (PDT) From: David Miller <davem@...emloft.net> To: johannes@...solutions.net Cc: joe@...ches.com, netdev@...r.kernel.org Subject: Re: [PATCH net-2.6.24] introduce MAC_FMT/MAC_ARG From: Johannes Berg <johannes@...solutions.net> Date: Mon, 27 Aug 2007 12:54:09 +0200 > -- change macros to -- > #define MAC_FMT "%s" > #define MAC_ARG(a) ({char __buf[18]; print_mac(a, buf); __buf}) > > I'm not sure we'd want that, but at the time you said it made the kernel > significantly smaller and I doubt there's a performance problem with it > (who prints mac addresses regularly?) I don't think this works. The scope of the __buf[18] array is inside of that MAC_ARG() expression, which will be fully evaluated before constructing the argument to printk(). Therefore printk() will be passed what is essentially a stale stack pointer. You'd need something like a "MAC_BUF buf;" all the callers need to declare, and a new "buf" argument to MAC_ARG(). If this was the goal, there are better approches to this, how about just calling: print_mac(dev->dev_addr); Sure, we'll have to split up printk() calls, but in the end it's likely still smaller and better. And I think it's much cleaner than this macro stuff. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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