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Date: Sun, 18 Jun 2006 10:42:18 -0700
From: "Randy.Dunlap" <rdunlap@xenotime.net>
To: sturmflut@lieberbiber.de
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 2/3] vdso: improve print_fatal_signals support by adding
 memory maps
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On Sun, 18 Jun 2006 15:25:35 +0200 Simon Raffeiner wrote:

> Am Sonntag, 18. Juni 2006 07:58 schrieben Sie:
> > On Sat, 17 Jun 2006 21:58:18 -0700
> >
> > "Randy.Dunlap" <rdunlap@xenotime.net> wrote:
> > > On Sat, 17 Jun 2006 16:14:52 +0200 Simon Raffeiner wrote:
> > > > When compiling 2.6.17-rc6-mm2 (which contains this patch) my gcc 4.0.3
> > > > (Ubuntu 4.0.3-1ubuntu5) complains about "int len;" being used
> > > > uninitialized in print_vma(). AFAICS len is not initialized and then
> > > > passed to
> > > > pad_len_spaces(int len), which uses it for some calculations.
> > > >
> > > > I also noticed that similar code is used in fs/proc/task_mmu.c, where
> > > > show_map_internal() passes an uninitialised int len; to
> > > > pad_len_spaces(struct seq_file *m, int len).
> > >
> > > Ack both of those.  And both of them pass &len as a parameter to
> > > printk/seq_printf where it looks as though they want just <len>
> > > (after it has been initialized).
> >
> > printk("%n", &len) will initialise `len'.  gcc is being wrong again.
> 
> pad_len_spaces() is called in the following way:
> 
> 
> static int print_vma(struct vm_area_struct *vma)
> {
> 	int len;
> 
> 	(...)
> 
> 	pad_len_spaces(len);
> 
> 	(...)
> 
> 
> and is defined as:
> 
> 
> static void pad_len_spaces(int len)
> {
>        len = 25 + sizeof(void*) * 6 - len;
> 
>        if (len < 1)
>                len = 1;
> 
>        printk("%*c", len, ' ');
> }
> 
> 
> len is passed to pad_len_spaces() without initialization and is used for 
> calculations BEFORE printk() is called.

Nope, len is used after printk(..., &len) is called.
But I don't see how printk() inits len... ?  :(  Magic?

---
~Randy