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Date: Fri, 26 May 2023 23:20:37 +0600
From: NRK <nrk@...root.org>
To: musl@...ts.openwall.com
Subject: Re: [C23 const 1/2] C23: change bsearch to a macro that
respects the const contract
On Fri, May 26, 2023 at 01:29:31PM +0200, Nat! wrote:
> I think it's sort of obvious, that these macros increase code brittleness
> due to now multiple execution of macro arguments vs. a single execution in a
> function call.
It would be heavily surprising if the controlling expression of _Generic
was evaluated. Similar to `sizeof`, it only needs to know the type of
the expression and thus doesn't require evaluation (only exception being
VLAs in a sizeof).
And looking at cppreference, it seems that the controlling expression
indeed isn't evaluated: https://en.cppreference.com/w/c/language/generic#Notes
| The controlling-expression and the expressions of the selections that
| are not chosen are never evaluated.
However, there is one thing that I don't quite understand about this
patch:
> + void const*: (void const*)bsearch((K), (void const*)(B), (N), (S), (C)), \
What's with the `(void const*)(B)` cast? It's already determined to be
`void const *` via _Generic.
- NRK
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