Elipsis with array

[berte]

Hello folks,

I investigating kernel sources I coincided with this part:

struct irq_desc irq_desc[NR_IRQS] __cacheline_ali gned_in_smp = {
[0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,
.chip = &no_irq_chip ,
.handle_irq = handle_bad_irq,
.depth = 1,
.lock = __SPIN_LOCK_UNL OCKED(irq_desc->lock),
#ifdef CONFIG_SMP
.affinity = CPU_MASK_ALL
#endif
}
};

Q1- What is this part "[0 ... NR_IRQS-1]" ?
Q2- Elipsis using with arrays ?

Regards.

[Antoninus Twink]

Re: Elipsis with array

On 13 Oct 2008 at 10:23, berte wrote:

struct irq_desc irq_desc[NR_IRQS] __cacheline_ali gned_in_smp = {
[0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,

[snip]

>
Q1- What is this part "[0 ... NR_IRQS-1]" ?
Q2- Elipsis using with arrays ?

This is a GNU extension. See
<http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html>

[Antoninus Twink]

Re: Elipsis with array

On 13 Oct 2008 at 10:23, berte wrote:

struct irq_desc irq_desc[NR_IRQS] __cacheline_ali gned_in_smp = {
[0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,

[snip]

>
Q1- What is this part "[0 ... NR_IRQS-1]" ?
Q2- Elipsis using with arrays ?

This is a GNU extension. See
<http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html>

[Wolfgang Draxinger]

Re: Elipsis with array

berte wrote:

Hello folks,
>
I investigating kernel sources I coincided with this part:
>
struct irq_desc irq_desc[NR_IRQS] __cacheline_ali gned_in_smp =
{ [0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,
.chip = &no_irq_chip ,
.handle_irq = handle_bad_irq,
.depth = 1,
.lock = __SPIN_LOCK_UNL OCKED(irq_desc->lock),
#ifdef CONFIG_SMP
.affinity = CPU_MASK_ALL
#endif
}
};
>
Q1- What is this part "[0 ... NR_IRQS-1]" ?
Q2- Elipsis using with arrays ?

Those are GNU extensions to the GCC, to ease the static
initialization of structures. You find them to be used
throughout large parts of the Linux kernel sources and their use
is highly encouraged to enhance readability.

See the documentation here:

http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Designated-Inits.html#Designated-Inits

Wolfgang Draxinger
--
E-Mail address works, Jabber: hexarith@jabber .org, ICQ: 134682867

[Martien Verbruggen]

Re: Elipsis with array

On Mon, 13 Oct 2008 03:23:31 -0700 (PDT),
berte <behzaterte@gma il.comwrote:

Hello folks,
>
I investigating kernel sources I coincided with this part:
>
struct irq_desc irq_desc[NR_IRQS] __cacheline_ali gned_in_smp = {
[0 ... NR_IRQS-1] = {

That's not standard C, but a gcc extension to initialise a range of
elements to the same value.

Check the gcc manual, under 'C Extensions' - 'Designated Inits'.

Martien
--
|
Martien Verbruggen |
| The gene pool could use a little chlorine.
|

[berte]

Re: Elipsis with array

On 13 Ekim, 13:52, Martien Verbruggen <m...@tradingpo st.com.auwrote:

On Mon, 13 Oct 2008 03:23:31 -0700 (PDT),
        berte <behzate...@gma il.comwrote:
>

Hello folks,

>

I investigating kernel sources I coincided with this part:

>

struct irq_desc irq_desc[NR_IRQS] __cacheline_ali gned_in_smp = {
   [0 ... NR_IRQS-1] = {

>
That's not standard C, but a gcc extension to initialise a range of
elements to the same value.
>
Check the gcc manual, under 'C Extensions' - 'Designated Inits'.
>
Martien
--
                        |
Martien Verbruggen      |
                        | The gene pool could usea little chlorine.
                        |

Thank you all. I got it :-)

Regards,
berte

[Ben Bacarisse]

Re: Elipsis with array

jacob navia <jacob@nospam.c omwrites:

berte wrote:

>>
>I investigating kernel sources I coincided with this part:
>>
>struct irq_desc irq_desc[NR_IRQS] __cacheline_ali gned_in_smp = {
> [0 ... NR_IRQS-1] = {
> .status = IRQ_DISABLED,
> .chip = &no_irq_chip ,
> .handle_irq = handle_bad_irq,
> .depth = 1,
> .lock = __SPIN_LOCK_UNL OCKED(irq_desc->lock),
>#ifdef CONFIG_SMP
> .affinity = CPU_MASK_ALL
>#endif
> }
>};
>>
>Q1- What is this part "[0 ... NR_IRQS-1]" ?
>Q2- Elipsis using with arrays ?
>>

>
This is a gnu extension. In

http://gcc.gnu.org/onlinedocs/gcc-2.95.3/gcc_4.html#SEC88

you can read:
4.20 Labeled Elements in Initializers

<snip quote from old manual>

By quoting such an old manual you obscure what is C99 and what is an
extension. The newer version makes it much clearer.

http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Designated-Inits.html#Designated-Inits

--
Ben.