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    SubjectRe: [PATCH 6/8]i2c:i2c_core Fix warning: variable 'dummy' set but not used
    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@gmail.com>
    >>
    >> ---
    >> 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)
    >> mutex_lock(&core_lock);
    >> dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap,
    >> __process_new_adapter);
    >> + if(!dummy)
    >> + dummy = 0;
    >
    > One word: scripts/checkpatch.pl
    >
    > 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:

    BUG_ON(dummy != WHAT_IT_SHOULD_BE);

    or

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


    or

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

    .
    .
    .

    i_really_know_what_i_am_doing(dummy);



    David Daney



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