Date: Fri, 25 Jul 2008 05:41:42 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Adrian Bunk <bunk@kernel.org>, Andrea Righi <righi.andrea@gmail.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: __weak vs ifdef
Message-Id: <20080725054142.372f1c03.akpm@linux-foundation.org>
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On Fri, 25 Jul 2008 06:24:54 -0600 Matthew Wilcox <matthew@wil.cx> wrote:

> On Fri, Jul 25, 2008 at 02:34:55AM -0700, Andrew Morton wrote:
> > We should make arch_pick_mmap_layout __weak and nuke that ifdef.
> 
> I strongly disagree.  I find it makes it harder to follow code flow
> when __weak functions are involved.  Ifdefs are ugly, no question, but
> they're easier to grep for, see when they'll be defined and know which of
> the arch_pick_mmap_layout() functions will be called.  __weak certainly
> has its uses (eg the sys_ni_syscall is great) but I find it's becoming
> overused.
> 
> My basic point here is that __weak makes the code easier to write but
> harder to read, and we're supposed to be optimising for easier to read.
> 

If you see

void __weak arch_foo(...)

and can't immediately work out what's going on then converting it to an
ifdef maze won't save you.

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