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    SubjectRe: [PATCH] [DISCUSS] Make the variable NULL after freeing it.
    Date
    Ingo Oeser <ioe-lkml@rameria.de> writes:

    > Hi,
    >
    > On Monday, 1. January 2007 07:37, Amit Choudhary wrote:
    >> --- Ingo Oeser <ioe-lkml@rameria.de> wrote:
    >> > #define kfree_nullify(x) do { \
    >> > if (__builtin_constant_p(x)) { \
    >> > kfree(x); \
    >> > } else { \
    >> > typeof(x) *__addr_x = &x; \
    >
    > Ok, I should change that line to
    > typeof(x) *__addr_x = &(x); \
    >
    >> > kfree(*__addr_x); \
    >> > *__addr_x = NULL; \
    >> > } \
    >> > } while (0)
    >> >
    >> > Regards
    >> >
    >> > Ingo Oeser
    >> >
    >>
    >> This is a nice approach but what if someone does kfree_nullify(x+20).
    >
    > Then this works, because the side effect (+20) is evaluated only once.

    It's not a side effect, it's a non-lvalue, and you can't take the address
    of a non-lvalue.

    Andreas.

    --
    Andreas Schwab, SuSE Labs, schwab@suse.de
    SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
    PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
    "And now for something completely different."
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