Re: [Qemu-devel] [PATCH] HACKING: Clarify the paragraph about typedefs

[Paolo Bonzini]

On 11/01/19 09:42, Thomas Huth wrote:
>  2.3. Typedefs
> -Typedefs are used to eliminate the redundant 'struct' keyword.
> +Typedefs can be used to eliminate the redundant 'struct' keyword. This is
> +especially helpful for common types that are used all over the place. Since
> +certain C compilers choke on duplicated typedefs, you should avoid them and
> +declare a typedef only in one header file. For common types, you can use
> +"include/qemu/typedefs.h" for example. Note that it is also perfectly fine to
> +use forward struct definitions without typedefs for references in headers
> +to avoid the problem with duplicated typedefs.
>  

I agree 100% with the wording after "Since".  However, I think the first
part should be made stronger, not weaker.

Typedefs are use to eliminate the redundant 'struct' keyword, since type
names have a different style than other identifiers ("CamelCase" versus
"snake_case").  Each struct should have a CamelCase name and a
corresponding typedef.

Since certain C compilers choke on duplicated typedefs, you should avoid
them and declare a typedef only in one header file.  For common types,
you can use "include/qemu/typedefs.h" for example.  However, as a metter
of convenience it is also perfectly fine to use forward struct
definitions instead of typedefs in headers and function prototypes; this
avoids problems with duplicated typedefs and reduces the need to include
headers from other headers.

And, I would move it to CODING_STYLE since we are at it. :)

Paolo