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Re: [Gnucap-devel] C question

From: Galen Seitz
Subject: Re: [Gnucap-devel] C question
Date: Mon, 19 Feb 2007 08:36:42 -0800
User-agent: Thunderbird (X11/20061222)

al davis wrote:
I ran into this in ngspice code ...

A structure ....

typedef struct SPICEdev {
int (*DEVparam)(int,IFvalue*,GENinstance*,IFvalue *); int (*DEVmodParam)(int,IFvalue*,GENmodel*); int (*DEVload)(GENmodel*,CKTcircuit*); int (*DEVsetup)(SMPmatrix*,GENmodel*,CKTcircuit*,int*); } SPICEdev;
is initialized like this ....

SPICEdev CCCSinfo = {
    DEVparam      : CCCSparam,
    DEVmodParam   : NULL,
    DEVload       : CCCSload,
    DEVsetup      : CCCSsetup

I would expect this (as it is in Spice 3f5) ....

SPICEdev CCCSinfo = {

The way it is done in ngspice is certainly an improvement, but I could not find any documentation for that syntax. It obviously works, at least with gcc. Is this a gcc extension? Can someone point me to some official documentation?

I am not looking for an explanation of how this feature works and why to use it. It is obvious to me. I am looking for a reference to official documentation. It is a good feature, that I would like to use, but I will only use it if it is part of the official language.

Using a colon in an initializer is an obsolete GCC syntax.  C99
now allows for designated initializers.  See

In a structure initializer, specify the name of a field to initialize with 
`.fieldname =' before the element value. For example, given the following 

    struct point { int x, y; };

the following initialization

    struct point p = { .y = yvalue, .x = xvalue };

is equivalent to

    struct point p = { xvalue, yvalue };

Another syntax which has the same meaning, obsolete since GCC 2.5, is 
`fieldname:', as shown here:

    struct point p = { y: yvalue, x: xvalue };


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