Elipsis with array

[berte]

Hello folks,

I investigating kernel sources I coincided with this part:

struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
[0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,
.chip = &no_irq_chip,
.handle_irq = handle_bad_irq,
.depth = 1,
.lock = __SPIN_LOCK_UNLOCKED(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]

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

struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_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]

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

struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_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]

berte wrote:

Hello folks,

I investigating kernel sources I coincided with this part:

struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp =
{ [0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,
.chip = &no_irq_chip,
.handle_irq = handle_bad_irq,
.depth = 1,
.lock = __SPIN_LOCK_UNLOCKED(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....signated-Inits

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

[Martien Verbruggen]

On Mon, 13 Oct 2008 03:23:31 -0700 (PDT),
berte <be********@gmail.comwrote:

Hello folks,

I investigating kernel sources I coincided with this part:

struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_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]

On 13 Ekim, 13:52, Martien Verbruggen <[e-mail]:

On Mon, 13 Oct 2008 03:23:31 -0700 (PDT),
* * * * berte <[e-mail]:

Hello folks,

I investigating kernel sources I coincided with this part:

struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_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]

jacob navia <ja***@nospam.comwrites:

berte wrote:

>>
I investigating kernel sources I coincided with this part:

struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
[0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,
.chip = &no_irq_chip,
.handle_irq = handle_bad_irq,
.depth = 1,
.lock = __SPIN_LOCK_UNLOCKED(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....c_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....signated-Inits

--
Ben.