linux code, about array initialization.

[Anonymousgoogledeja]

hi all,

while I read the code from linux sources.

I read the statement

static const struct iw_ioctl_descri ption standard_ioctl[] = {
[SIOCSIWCOMMIT - SIOCIWFIRST] = {
.header_type = IW_HEADER_TYPE_ NULL,
},
...
};

I have never read such code. normaly, I will write the code as :

static const struct iw_ioctl_descri ption standard_ioctl[] = {
{
.header_type = IW_HEADER_TYPE_ NULL,
},
...
};

anyone would help me? thanks

[Keith Thompson]

"Anonymousgoogl edeja" <as*******@hotm ail.com> writes:

while I read the code from linux sources.

I read the statement

static const struct iw_ioctl_descri ption standard_ioctl[] = {
[SIOCSIWCOMMIT - SIOCIWFIRST] = {
.header_type = IW_HEADER_TYPE_ NULL,
},
...
};

I have never read such code. normaly, I will write the code as :

static const struct iw_ioctl_descri ption standard_ioctl[] = {
{
.header_type = IW_HEADER_TYPE_ NULL,
},
...
};

The [SIOCSIWCOMMIT - SIOCIWFIRST] specifies an array index.
Presumably SIOCSIWCOMMIT-SIOCIWFIRST is an integer constant
expression.

By specifying the index values, you don't necessarily have to give the
array elements in order.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Anonymousgoogledeja]

I wonder whether it's gcc specific or ANSI std specific?
Keith Thompson wrote:

"Anonymousgoogl edeja" <as*******@hotm ail.com> writes:

while I read the code from linux sources.

I read the statement

static const struct iw_ioctl_descri ption standard_ioctl[] = {
[SIOCSIWCOMMIT - SIOCIWFIRST] = {
.header_type = IW_HEADER_TYPE_ NULL,
},
...
};

I have never read such code. normaly, I will write the code as :

static const struct iw_ioctl_descri ption standard_ioctl[] = {
{
.header_type = IW_HEADER_TYPE_ NULL,
},
...
};

The [SIOCSIWCOMMIT - SIOCIWFIRST] specifies an array index.
Presumably SIOCSIWCOMMIT-SIOCIWFIRST is an integer constant
expression.

By specifying the index values, you don't necessarily have to give the
array elements in order.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Keith Thompson]

"Anonymousgoogl edeja" <as*******@hotm ail.com> writes:

Keith Thompson wrote:

"Anonymousgoogl edeja" <as*******@hotm ail.com> writes:

> while I read the code from linux sources.
>
> I read the statement
>
> static const struct iw_ioctl_descri ption standard_ioctl[] = {
> [SIOCSIWCOMMIT - SIOCIWFIRST] = {
> .header_type = IW_HEADER_TYPE_ NULL,
> },
> ...
> };
>
> I have never read such code. normaly, I will write the code as :
>
> static const struct iw_ioctl_descri ption standard_ioctl[] = {
> {
> .header_type = IW_HEADER_TYPE_ NULL,
> },
> ...
> };

The [SIOCSIWCOMMIT - SIOCIWFIRST] specifies an array index.
Presumably SIOCSIWCOMMIT-SIOCIWFIRST is an integer constant
expression.

By specifying the index values, you don't necessarily have to give the
array elements in order.

I wonder whether it's gcc specific or ANSI std specific?

Please don't top-post. Your reply goes below the quoted text, so the
entire article can be read from top to bottom.

Designators in initializers (including both the ".member=va lue" and
"[index]=value" forms) are a new feature in C99. (The term "ANSI" is
ambiguous; strictly speaking the current 1999 ISO standard is the ANSI
standard, but the term "ANSI" is commonly used to refer to the
1989/1990 ANSI/ISO standard.)

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Emmanuel Delahaye]

Anonymousgoogle deja a écrit :

while I read the code from linux sources.

I read the statement

static const struct iw_ioctl_descri ption standard_ioctl[] = {
[SIOCSIWCOMMIT - SIOCIWFIRST] = {
.header_type = IW_HEADER_TYPE_ NULL,
},
...
};

I have never read such code. normaly, I will write the code as :

static const struct iw_ioctl_descri ption standard_ioctl[] = {
{
.header_type = IW_HEADER_TYPE_ NULL,
},
...
};

anyone would help me? thanks

Read again. 'iw_ioctl_descr iption standard_ioctl' is an *array* of
structure... For an 'absolute' initializing (C99), you also need the index.

--
C is a sharp tool