Re: [musl] [C23 const 1/2] C23: change bsearch to a macro that respects the const contract

[Nat! <nat@mulle-kybernetik.com>]

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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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