Re: [PATCH 6/8]i2c:i2c_core Fix warning: variable 'dummy' set butnot used

From: David Daney
Date: Mon Jun 14 2010 - 17:29:10 EST

On 06/14/2010 01:53 PM, Jean Delvare wrote:
Hi Justin,

On Mon, 14 Jun 2010 13:26:46 -0700, Justin P. Mattock wrote:
could be a right solution, could be wrong
here is the warning:
CC drivers/i2c/i2c-core.o
drivers/i2c/i2c-core.c: In function 'i2c_register_adapter':
drivers/i2c/i2c-core.c:757:15: warning: variable 'dummy' set but not used

Signed-off-by: Justin P. Mattock<justinmattock@xxxxxxxxx>

drivers/i2c/i2c-core.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 1cca263..79c6c26 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -794,6 +794,8 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap,
+ if(!dummy)
+ dummy = 0;

One word: scripts/

In other news, the above is just plain wrong. First we force people to
read the result of bus_for_each_drv() and then when they do and don't
need the value, gcc complains, so we add one more layer of useless
code, which developers and possibly tools will later wonder and
complain about? I can easily imagine that a static code analyzer would
spot the above code as being a potential bug.

Let's stop this madness now please.

Either __must_check goes away from bus_for_each_drv() and from every
other function which raises this problem, or we must disable that new
type of warning gcc 4.6.0 generates. Depends which warnings we value
more, as we can't sanely have both.

That is the crux of the whole thing. Putting in crap to get rid of the __must_check warning someone obviously wanted to provoke is just plain wrong.

I don't know what the answer is, but in addition to your suggestion of removing the __must_check, you might try:



if (dummy != WHAT_IT_SHOULD_BE)
panic("nice message here);


static inline void i_really_know_what_i_am_doing(int arg)
* Trick the compiler because we don't want to
* handle error conditions.



David Daney

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