Strange sintax

[InuY4sha]

Hi all
sorry.. I know this is a very mean question but I can't get the
following couple of lines:
static int dev_init(struct net_device *dev);
struct net_device my_device = { init: dev_init, };
To me it looks something like defining a function and creating a
structure that stores a label referencing that function.. what's the
scope behind this ?
Also I don't get the comma after "dev_init"...
Can somebody explain me this sintax please ?

Thanks in advance,
RM

 

[Walter Roberson]

sorry.. I know this is a very mean question but I can't get the
following couple of lines:
static int dev_init(struct net_device *dev);
struct net_device my_device = { init: dev_init, };
To me it looks something like defining a function and creating a
structure that stores a label referencing that function.. what's the
scope behind this ?

I suspect it is C99 and it means that the my_device field
named 'init' is to be initialized to the function pointer dev_init .

Also I don't get the comma after "dev_init"...
Can somebody explain me this sintax please ?

C99 allows an extra comma at the end of an initialization list.
It tends to make code easier to maintain.

 

[WANG Cong]

Hi all
sorry.. I know this is a very mean question but I can't get the
following couple of lines:
static int dev_init(struct net_device *dev);
struct net_device my_device = { init: dev_init, };
To me it looks something like defining a function and creating a
structure that stores a label referencing that function.. what's the
scope behind this ?

It's not a label, it's a field name. But this is not standard, and also
deprecated by gcc. You should use the standard way:

struct net_device my_device = { .init = dev_init, };

Also I don't get the comma after "dev_init"...
Can somebody explain me this sintax please ?

Just like other initialization, the last comma doesn't matter here.

 

[WANG Cong]

I suspect it is C99 and it means that the my_device field
named 'init' is to be initialized to the function pointer dev_init .

No. C99 uses the ".identifier" form.

And yes, 'init' should be a member of the net_device struct, and a function
pointer of that type like dev_init().

 

[Ben Bacarisse]

I suspect it is C99 and it means that the my_device field
named 'init' is to be initialized to the function pointer dev_init .

The C99 syntax for a designated initializer is:

struct net_device my_device = { .init = dev_init, };

I think the "field_name:" form is a GCCism.

 

[Ben Pfaff]

C99 allows an extra comma at the end of an initialization list.

So does C89.

 

[user923005]

So does C89.

There are some compilers that will blow a gasket, though (e.g. those
for OpenVMS).

 

[Ben Pfaff]

There are some compilers that will blow a gasket, though (e.g. those
for OpenVMS).

Then they aren't C89 compilers.

C99 did add the ability to add a trailing comma in one context:
within the list of enumerated values in an enum definition.

 

[Dann Corbit]

Then they aren't C89 compilers.

True enough, but I have to use them.
;-)