Messages in this thread | | | Date | Tue, 15 Aug 2023 13:28:37 +0200 | Subject | Re: cleanup: Make no_free_ptr() __must_check | From | Rasmus Villemoes <> |
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On 15/08/2023 12.52, Peter Zijlstra wrote: > > recent discussion brought about the realization that it makes sense for > no_free_ptr() to have __must_check semantics in order to avoid leaking > the resource. >
> +static inline __must_check void * __no_free_ptr(void **pp) > +{ void *p = *pp; *pp = NULL; return p; } > + > #define no_free_ptr(p) \ > - ({ __auto_type __ptr = (p); (p) = NULL; __ptr; }) > + (({ void * __maybe_unused ___t = (p); }), \ > + ((typeof(p))__no_free_ptr((void **)&(p))))
So this does seem to work as advertised, but it could perhaps use some comments. Because at first I read this as one big statement expression, and I had this memory of a __must_check function call being the last expression in such had no effect at all [1]. But this is actually a comma expression.
Also, isn't it more complicated than necessary? Can we get rid of the inner stmt expr and tmp var by just making it
((void) (p), ((typeof(p))__no_free_ptr((void **)&(p)))
which is more or less the whole reason comma expressions is a thing.
Rasmus
[1] https://lore.kernel.org/lkml/6d190601-68f1-c086-97ac-2ee1c08f5a34@rasmusvillemoes.dk/
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