Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 17 Apr 2018 17:07:04 -0700 | Subject | Re: [PATCH v3 1/6] ilog2: create truly constant version for sparse |
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On Tue, Apr 17, 2018 at 4:35 PM, Martin Wilck <mwilck@suse.com> wrote: > Sparse emits errors about ilog2() in array indices because of the use of > __ilog2_32() and __ilog2_64(),
If sparse warns about it, then presumably gcc with -Wvla warns about it too?
And if thats the case, then __builtin_constant_p() and a ternary operation isn't good enough, because gcc -Wvla is even more anal than sparse is.
Which is why we have that __is_constexpr() magic for min/max().
So I suspect that what you'd want is
#define ilog2(n) \ __builtin_choose_expr(__is_constexpr(n), \ const_ilog2(n), \ __builtin_choose_expr(sizeof(n) <= 4, \ __ilog2_u32(n), \ __ilog2_u64(n)))
or something. Hmm?
Linus
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