Re: [PATCH 1/3] ipc: Convert handmade 'max' to max().

From: Richard Knutsson
Date: Fri Jan 04 2008 - 01:47:01 EST


Sorry for the late response, have been away during the holidays.

Andrew Morton wrote:
On Mon, 17 Dec 2007 03:35:55 +0100 (MET) Richard Knutsson <ricknu-0@xxxxxxxxxxxxxx> wrote:

Convert handmade 'max' to max().

...

--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -473,7 +473,7 @@ asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
up_read(&msg_ids(ns).rw_mutex);
if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
return -EFAULT;
- return (max_id < 0) ? 0 : max_id;
+ return max(max_id, 0);

I don't think I like that much.

I tend to think of max() as being an arithmetic sort of thing: pick the
largest of two scalars.

But the code which you're changing is a _logical_ operation. It says "if
ipc_get_maxid() returned an error, then return zero. Otherwise return
whatever ipc_get_maxid() returned".

Yes, max() will do the right thing here, but I think it's a bit of weird
trick?


I mean, if ipc_get_maxid() were a better function, it would return a -ve
errno when something failed rather than the present dopey hard-coded -1. In which case the code would read

return IS_ERR_VALUE(max_id) ? 0 : max_id;

in which case, converting it to max() would be even less appropriate. If
you see what I mean...
Yes, have to agree. Were too quick with the changing...

Thanks
Richard Knutsson

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