C99: Suggestions for style(9)

[Christoph Mallon]

M. Warner Losh schrieb:
> In message: <20090430233648.GA95360 at keira.kiwi-computer.com>
>             "Rick C. Petty" <rick-freebsd2008 at kiwi-computer.com> writes:
> : On Thu, Apr 30, 2009 at 09:02:26AM -0600, M. Warner Losh wrote:
> : > 
> : > This is the biggest one, and I think it may be too soon.  Also, we
> : > need to be careful on the initialization side of things because we
> : > currently have a lot of code that looks like:
> : > 
> : > 
> : > 	struct foo *fp;
> : > 	struct bar *bp;
> : > 
> : > 	fp = get_foo();
> : > 	if (!fp) return;
> : > 	bp = fp->bp;
> : > 
> : > this can't easily be translated to the more natural:
> : > 
> : > 	struct foo *fp = get_foo();
> : > 	struct bar *bp = fp->bp;
> : > 
> : > since really you'd want to write:
> : > 
> : > 	struct foo *fp = get_foo();
> : > 	if (!fp) return;
> : > 	struct bar *bp = fp->bp;
> : > 
> : > which isn't legal in 'C'.
> : 
> : I thought we were talking about C99, in which case this is perfectly legal.
> : I certainly use it all the time in my C99 code.
> 
> Hmmm, looks like that was added.  That's ugly as C++...

I do not think, this is ugly. On the contrary, it aids maintainability, 
because it reduces the scope of variables. Also quite some variables are 
only initialised and not changed afterwards, so it's nice to have the 
declaration and the only assignment in a single place. IMO this is a 
quite natural style, because you don't have anything in the code, before 
it is needed: Get the first pointer; if something is wrong, bail out; 
get the second pointer - the second pointer does not (textually) exist 
before it is needed.

> : And I thought this was the point of this discussion, to be able to declare
> : variables when you first use them.
> 
> That's one of the proposed changes, which I think is a mistake and
> would cause the most code churn.  And it isn't one of the items that's
> being discussed: only moving variables into inner scopes is on the
> table...

No, this is not what I intended. The idea is to limit the scope of local 
variables as much as is sensible. Maybe I should have been more 
explicit. On the other hand, I also did not mention that it is just 
about moving to the start of inner block statements.

	Christoph