netdev - RE: [PATCH] net: usb: initialize tmp in dm9601.c to avoid warning

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Message-ID: <AE90C24D6B3A694183C094C60CF0A2F6026B7116@saturn3.aculab.com>
Date:	Fri, 18 Jan 2013 10:07:20 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"David Miller" <davem@...emloft.net>, <jacmet@...site.dk>
Cc:	<sque@...omium.org>, <netdev@...r.kernel.org>, <msb@...omium.org>
Subject: RE: [PATCH] net: usb: initialize tmp in dm9601.c to avoid warning

> > Sure, I just wondered as the code hasn't changed in 5+ years, and the
> > function that gets called is defined just above, so the compiler should
> > be able to figure it out.
> 
> Nothing guarentees that a piece of memory passed into an external
> function has it's contents initialized completely by that function.
> 
> The compiler can't see what usbnet_read_cmd() does with the memory
> behind the 'data' pointer argument.  So it makes the only assumption
> it can make, which is that 'tmp' might be uninitialized.

Possibly the called function is being inlined, then the analysis
knows that some paths don't assign a value.
When it isn't inlined it assumes the value is always modified.

	David



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