--- Ingo Oeser <[email protected]> wrote:
> On Sunday, 31. December 2006 14:38, Bernd Petrovitsch wrote:
> > That depends on the decision/definition if (so called) "double free" is
> > an error or not (and "free(NULL)" must work in POSIX-compliant
> > environments).
>
> A double free of non-NULL is certainly an error.
> So the idea of setting it to NULL is ok, since then you can
> kfree the variable over and over again without any harm.
>
> It is just complicated to do this side effect free.
>
> Maybe one should check for builtin-constant and take the address,
> if this is not an builtin-constant.
>
> sth, like this
>
> #define kfree_nullify(x) do { \
> if (__builtin_constant_p(x)) { \
> kfree(x); \
> } else { \
> 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).
I decided to keep it simple. If someone is calling kfree_nullify() with anything other than a
simple variable, then they should call kfree(). But definitely an approach that takes care of all
situations is the best but I cannot think of a macro that can handle all situations. The simple
macro that I sent earlier will catch all the other usage at compile time. Please let me know if I
have missed something.
-Amit
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