linux-kernel - __weak vs ifdef

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Message-ID: <20080725122454.GE6701@parisc-linux.org>
Date:	Fri, 25 Jul 2008 06:24:54 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Adrian Bunk <bunk@...nel.org>,
	Andrea Righi <righi.andrea@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: __weak vs ifdef

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.

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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