Re: [PATCH v3 6/7] stdlib: Implement introsort with qsort

[Alexander Monakov via Libc-alpha <libc-alpha@sourceware.org>]

On Fri, 3 Sep 2021, Adhemerval Zanella via Libc-alpha wrote:

> @@ -235,6 +305,9 @@ _quicksort (void *const pbase, size_t total_elems, size_t size,
>    else
>      swap_func = SWAP_BYTES;
>  
> +  /* Maximum depth before quicksort switches to heapsort.  */
> +  size_t depth = 2 * (CHAR_BIT - 1 - __builtin_clzl (total_elems));
> +

This doesn't look right, the expression in parenthesis is usually negative,
conversion to size_t wraps around and you make 'depth' a huge positive value.
The first term probably should have been 'CHAR_BIT * sizeof(size_t)'.

Does this mean that heapsort fallback was not exercised in testing?

Also, is it certain at that point that total_elems is nonzero? __builtin_clzl
is undefined for a zero argument.

Alexander