On 3/31/10 6:53 AM, Guilhem Bichot wrote:
> Hello,
>
> this has been debated in the past but not in the coding style committee
> recently, so here it is.
>
> http://forge.mysql.com/wiki/MySQL_Internals_Coding_Guidelines says
> "Put a comment in front of its subject. In particular, function and
> method comments should be placed in front of implementation rather than
> declaration. Class comments should be put in front of class declaration."
>
> Even though I obey the rule, and enforce it on others when I'm code
> reviewer, I would like the rule to be changed at least for class
> methods: I would like their comment to be in front of the declaration
> (so inside the class declaration). In short and approximatively: in the
> ".h" file, not in the ".cc" file.
>
> Like this:
> class C
> {
> /** comment (@param etc @retval etc) */
> method();
> }
>
> My reasons:
> 1) imagine a class with members, pure virtual methods, inline methods,
> and non-inline methods. The three first have their definition in the
> class's declaration, and only the fourth has its definition in the .cc
> file. Then the current rule suggests this:
>
> class C
> {
> member; /** comment */
> pure virtual method; /** comment */
> method; /** no comment, as definition is in .cc */
> inline_method { code }; /** comment */
> }
> and I find this inconsistent: only for "method" do you have to look up
> the comment in the .cc file.
>
> 2) if I want to help the API user, who in theory can ignore the
> implementation (the .cc) and concentrate on the API (the .h), it's
> better if descriptive comments are in the .h. The comment in the .h can
> tell what to give to the method and what to expect from it, that's all
> the API user needs to know.
>
> 3) it's also easier for design reviews: if descriptive comments are in
> the .h I can just paste the .h to the design reviewer, it makes a
> self-documenting design.
>
> I know the current rule is liked by some and has upset others, so I
> suggest this be discussed by the Coding style committee (note: I'm not
> in it anymore).
> Thanks!
>
I would like to suggest that it is made clear that documentation in a
header file does not exempt documentation in source files. IMHO, in the
headers (function prototype) we should document the function "interface"
-- that is, everything that is relevant to a user of the function (eg,
longer description, parameters, etc), and in the source file (function
definition), document implementation details (eg, shorter description
and the "guts" of the function, etc).
Regards,
Davi
