Date: Fri, 01 May 2009 08:37:12 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: christoph.mallon@gmx.de Cc: rick-freebsd2008@kiwi-computer.com, freebsd-hackers@FreeBSD.org Subject: Re: C99: Suggestions for style(9) Message-ID: <20090501.083712.396385864.imp@bsdimp.com> In-Reply-To: <20090501.081229.1359784281.imp@bsdimp.com> References: <20090430.183727.803597558.imp@bsdimp.com> <49FA8E88.1040905@gmx.de> <20090501.081229.1359784281.imp@bsdimp.com>
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In message: <20090501.081229.1359784281.imp@bsdimp.com>
M. Warner Losh <imp@bsdimp.com> writes:
: In message: <49FA8E88.1040905@gmx.de>
: Christoph Mallon <christoph.mallon@gmx.de> writes:
: : M. Warner Losh schrieb:
: : > In message: <20090430233648.GA95360@keira.kiwi-computer.com>
: : > "Rick C. Petty" <rick-freebsd2008@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
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