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Message-ID: <3a4f4a8e-9179-6606-e449-6fc2812d3525@mulle-kybernetik.com>
Date: Fri, 26 May 2023 13:29:31 +0200
From: Nat! <nat@...le-kybernetik.com>
To: musl@...ts.openwall.com
Subject: Re: [C23 const 1/2] C23: change bsearch to a macro that
respects the const contract
I can't help but comment on these changes. :)
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. Weighing this versus the loss of
const qualification (on my personal importance scale from 0-10a clear
0), it is not a worthwhile tradeoff.
Ciao
Nat!
Am 25.05.23 um 16:44 schrieb Jens Gustedt:
> This adds a macro interface to stdlib that has an additional cast of
> the return value to `void const*` for the case that the argument to
> the call was also const-qualified. Nothing changes for the function
> itself, only the identifier has to be protected with (), such that the
> macro does not expand for the function declaration or definition.
> ---
> include/stdlib.h | 12 +++++++++++-
> src/include/stdlib.h | 2 ++
> src/stdlib/bsearch.c | 2 +-
> 3 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/include/stdlib.h b/include/stdlib.h
> index 68ccd467..f5281777 100644
> --- a/include/stdlib.h
> +++ b/include/stdlib.h
> @@ -60,7 +60,17 @@ char *getenv (const char *);
>
> int system (const char *);
>
> -void *bsearch (const void *, const void *, size_t, size_t, int (*)(const void *, const void *));
> +void * (bsearch) (const void *, const void *, size_t, size_t, int (*)(const void *, const void *));
> +#if __STDC_VERSION__ > 201112L
> +# define bsearch(K, B, N, S, C) \
> + _Generic( \
> + /* ensure conversion to a void pointer */ \
> + 1 ? (B) : (void*)1, \
> + void const*: (void const*)bsearch((K), (void const*)(B), (N), (S), (C)), \
> + /* volatile qualification of *B is an error for this call */ \
> + default: bsearch((K), (B), (N), (S), (C)) \
> +)
> +#endif
> void qsort (void *, size_t, size_t, int (*)(const void *, const void *));
>
> int abs (int);
> diff --git a/src/include/stdlib.h b/src/include/stdlib.h
> index 812b04de..f0b03df9 100644
> --- a/src/include/stdlib.h
> +++ b/src/include/stdlib.h
> @@ -16,4 +16,6 @@ hidden void *__libc_calloc(size_t, size_t);
> hidden void *__libc_realloc(void *, size_t);
> hidden void __libc_free(void *);
>
> +#undef bsearch
> +
> #endif
> diff --git a/src/stdlib/bsearch.c b/src/stdlib/bsearch.c
> index fe050ea3..4f62ea37 100644
> --- a/src/stdlib/bsearch.c
> +++ b/src/stdlib/bsearch.c
> @@ -1,6 +1,6 @@
> #include <stdlib.h>
>
> -void *bsearch(const void *key, const void *base, size_t nel, size_t width, int (*cmp)(const void *, const void *))
> +void *(bsearch)(const void *key, const void *base, size_t nel, size_t width, int (*cmp)(const void *, const void *))
> {
> void *try;
> int sign;
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