Re: [PATCH 3/5] isdn: fix integer as NULL pointer warning

From: Linus Torvalds
Date: Fri May 23 2008 - 11:09:40 EST

On Thu, 22 May 2008, Harvey Harrison wrote:
> len += sprintf(page+len, "%-16s %s\n", "type", s);
> - if ((s = cinfo->version[VER_DRIVER]) != 0)
> + if ((s = cinfo->version[VER_DRIVER]) != NULL)
> len += sprintf(page+len, "%-16s %s\n", "ver_driver", s);

For thigns like this (ie testing an assignment), I personally much prefer

s = cinfo->version[VER_DRIVER];
if (s)
len += sprintf(page+len, "%-16s %s\n", "ver_driver", s);

over the uglier and unreadable version.

IOW, testing assignments is good only when:

- you have to do it because of syntax (ie notably in a "while()" loop)

- there's some reason you want it to be a single statement (eg doing a
macro or other thing)

- of the assignment is really simple, and the test is not against NULL or

The reason for that "the test is not against NULL or zero" is that testing
for NULL and 0 is better done with just a "if (x)", and in an assignment
that just means either (a) a incomprehensible extra parenthesis just to
shut the compiler up or (b) changing the simple test into a stupid test
(ie doing "if (x != NULL)").

(b) is much preferable to (a), but just doing it as two statements is
much preferable to either!

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