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linux-os (Dick Johnson) napsal(a):
> On Mon, 1 May 2006, Alexey Dobriyan wrote:
>
>> On Mon, May 01, 2006 at 04:00:09PM +0200, Jan Engelhardt wrote:
>>>> +Please don't use things like "vps_t".
>>>> +It's a _mistake_ to use typedef for structures and pointers. When you see a
>>>> + vps_t a;
>>>> +in the source, what does it mean?
>>>> +In contrast, if it says
>>>> + struct virtual_container *a;
>>>> +you can actually tell what "a" is.
>>>> +
>>>> +Lots of people think that typedefs "help readability". Not so. They are
>>>> +useful only for:
>>> [...]
>>>
>>> What about task_t vs struct task_struct? Both are used in the kernel.
>> task_t => struct task
>> struct task_struct => struct task
>>
>> Roughly 2765 hits :-\
>
> Yes, also 'current' is probably the most used. Any, since this
> has become a FAQ, maybe it's about time to put something in the
> Documentation?
>
> --- /usr/src/linux-2.6.16.4/Documentation/CodingStyle.orig 2006-05-01 10:17:03.000000000 -0400
> +++ /usr/src/linux-2.6.16.4/Documentation/CodingStyle 2006-05-01 10:37:09.000000000 -0400
> @@ -343,6 +343,33 @@
> Remember: if another thread can find your data structure, and you don't
> have a reference count on it, you almost certainly have a bug.
>
> + typedefs and and structs
> +
> +Typedefs should never be used for information hiding. In other words,
> +if a typedef defines an aggregate type, and the individual components
> +are accessed anywhere in the code, a typedef should not be used.
> +
> +An example of proper usage:
> +typedef struct opaque_type FILE; // In a header
> +
> + FILE *fp; // In a program block
> +
> +The type 'FILE' in this example is something that was defined in
> +a 'C' runtime library. The code uses pointers to this opaque type,
> +but never even knows, and doesn't care, what's inside that structure.
> +Therefore, FILE can have been defined using a typedef.
> +
> +An example of incorrect usage:
> +
> +typedef struct file_operations FO; // In a header
> +
> + FO fo; // In a program block
> + memset(&foo, 0x00, sizeof(foo));
> +
> +In this case, object FO contains structure members that will be
> +accessed by the code. It should not have been defined. Instead,
> +the structure name should have been used directly.
> +
>
> Chapter 11: Macros, Enums and RTL
>
>
>
> In case the M$ server mangles the patch, it's included as an attachment.
>
>
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
> New book: http://www.lymanschool.com
> _
>
>
>
> ****************************************************************
> The information transmitted in this message is confidential and may be privileged. Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited. If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to [email protected] - and destroy all copies of this information, including any attachments, without reading or disclosing them.
>
> Thank you.
>
>
> ------------------------------------------------------------------------
>
> --- /usr/src/linux-2.6.16.4/Documentation/CodingStyle.orig 2006-05-01 10:17:03.000000000 -0400
> +++ /usr/src/linux-2.6.16.4/Documentation/CodingStyle 2006-05-01 10:37:09.000000000 -0400
> @@ -343,6 +343,33 @@
> Remember: if another thread can find your data structure, and you don't
> have a reference count on it, you almost certainly have a bug.
>
> + typedefs and and structs
> +
> +Typedefs should never be used for information hiding. In other words,
> +if a typedef defines an aggregate type, and the individual components
> +are accessed anywhere in the code, a typedef should not be used.
> +
> +An example of proper usage:
> +typedef struct opaque_type FILE; // In a header
> +
> + FILE *fp; // In a program block
> +
> +The type 'FILE' in this example is something that was defined in
> +a 'C' runtime library. The code uses pointers to this opaque type,
> +but never even knows, and doesn't care, what's inside that structure.
> +Therefore, FILE can have been defined using a typedef.
> +
> +An example of incorrect usage:
> +
> +typedef struct file_operations FO; // In a header
> +
> + FO fo; // In a program block
You meant 'FO foo', didn't you?
> + memset(&foo, 0x00, sizeof(foo));
> +
> +In this case, object FO contains structure members that will be
> +accessed by the code. It should not have been defined. Instead,
> +the structure name should have been used directly.
> +
>
> Chapter 11: Macros, Enums and RTL
>
regards,
- --
Jiri Slaby www.fi.muni.cz/~xslaby
\_.-^-._ [email protected] _.-^-._/
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