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

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

[Harvey Harrison]

drivers/isdn/hysdn/hycapi.c:465:42: warning: Using plain integer as NULL pointer
drivers/isdn/hysdn/hycapi.c:467:44: warning: Using plain integer as NULL pointer
drivers/isdn/hysdn/hycapi.c:469:42: warning: Using plain integer as NULL pointer

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
---
 drivers/isdn/hysdn/hycapi.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/isdn/hysdn/hycapi.c b/drivers/isdn/hysdn/hycapi.c
index d3999a8..53f6ad1 100644
--- a/drivers/isdn/hysdn/hycapi.c
+++ b/drivers/isdn/hysdn/hycapi.c
@@ -462,11 +462,11 @@ static int hycapi_read_proc(char *page, char **start, off_t off,
 		default: s = "???"; break;
 	}
 	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);
-	if ((s = cinfo->version[VER_CARDTYPE]) != 0)
+	if ((s = cinfo->version[VER_CARDTYPE]) != NULL)
 		len += sprintf(page+len, "%-16s %s\n", "ver_cardtype", s);
-	if ((s = cinfo->version[VER_SERIAL]) != 0)
+	if ((s = cinfo->version[VER_SERIAL]) != NULL)
 		len += sprintf(page+len, "%-16s %s\n", "ver_serial", s);
     
 	len += sprintf(page+len, "%-16s %s\n", "cardname", cinfo->cardname);
-- 
1.5.5.1.579.g4e43

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

[Linus Torvalds]

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 
   zero.

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!

		Linus