C99: Suggestions for style(9)

[M. Warner Losh]

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.

Warner