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Date: Wed, 11 Mar 2009 18:23:08 +0100
Message-ID: <8763ig7z43.wl%vmayatsk@redhat.com>
From: Vitaly Mayatskikh <v.mayatskih@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Vitaly Mayatskikh <v.mayatskih@gmail.com>, linux-kernel@vger.kernel.org
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> On Wed, 11 Mar 2009, Vitaly Mayatskikh wrote:
> > 
> > (v)scnprintf says it should return 0 when size is 0, but doesn't do
> > so. Also size_t is unsigned, it can't be less then 0. Fix the code and
> > comments.
> 
> That is bogus.
> 
> The code really does (od "did"? Maybe you removed it) check for _smaller_ 
> than 0:

Well, (v)scnprintf says it returns 0 for size <= 0, but really returns
-1 for size == 0. I think, this code can't return 0 for size == 0:

	i=vsnprintf(buf,size,fmt,args);
	return (i >= size) ? (size - 1) : i;

Systemtap's script:

function test:long()
%{
        char tmp[256];
        long err;
        err = scnprintf(tmp, 0, "%lu", (long)128);
        THIS->__retvalue = err;
%}

probe begin
{
        printf("scnprintf returns %d\n", test());
}

stap -g scnprintf.stp
scnprintf returns -1

-- 
wbr, Vitaly