C99: Suggestions for style(9)

[M. Warner Losh]

In message: <20090501.081229.1359784281.imp at bsdimp.com>
            M. Warner Losh <imp at bsdimp.com> writes:
: In message: <49FA8E88.1040905 at gmx.de>
:             Christoph Mallon <christoph.mallon at gmx.de> writes:
: : 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.
: 
: It is ugly.  Hunting for declarations sucks, and it is one of the
: things I really like about BSD code is that I don't have to.
: 
: This is a religious point, and we're dangerously close to saying my
: religion is better than your religion.  I don't like this part of the
: proposal at all.  I can see the value in relaxing it for when you have
: a series of variables that are initialized, but relaxing it to the
: point where you intermix code and declarations goes way too far.  It
: is bad enough to have to deal with inner scopes, but tolerable.  It is
: intolerable to have to look for it anywhere in a big function.  It
: tends to encourage spaghetti code, which is one of the things that
: style(9) tries to discourage in many subtle ways.

This came off a little more absolute than I wanted.  I should have
added "in the absence of hard data..."

Warner