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Date: Mon, 29 Nov 2004 18:12:12 +0000
From: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
To: Jan Engelhardt <jengelh@linux01.gwdg.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: ppcfix.diff
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On Mon, Nov 29, 2004 at 06:44:14PM +0100, Jan Engelhardt wrote:
> >>  	if (!cpus_empty(keepmask)) {
> >> -		cpumask_t irqdest = { .bits[0] = openpic_read(&ISR[irq]->Destination) };
> >> +		cpumask_t irqdest;
> >> +		irqdest.bits[0] = openpic_read(&ISR[irq]->Destination);
> >
> >Not an equivalent replacement.  The former means "set irqdest.bits[0] to
> ><expression> and set the rest of fields/array elements in them to zero/null".
> 
> Really? I thought zero'ing only happens for static storage.

Two different issues - behaviour when no initializer is given and behaviour
when initializer does not cover everything.

IOW,

static int a1[4];		/* all zeroes, since it's non-auto */
static int a2[4] = {1,0,0,0}	/* 1 0 0 0, we have initialized them all */
static int a3[4] = {1}		/* 1 0 0 0, missing members are zeroed */
void f(void)
{
	int b1[4];		/* undefined contents */
	int b2[4] = {1,0,0,0}	/* 1 0 0 0, we have initialized them all */
	int b3[4] = {1}		/* 1 0 0 0, missing members are zeroed */

C99 6.7.8(21) and 6.7.8(10) deal with "not covers everything" and
"no initializer at all" resp.
-
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