[PATCH] Reduce memory size of tsearch red-black tree.

[Adhemerval Zanella]

> diff --git a/misc/tsearch.c b/misc/tsearch.c
> index ffb89ec..708239f 100644
> --- a/misc/tsearch.c
> +++ b/misc/tsearch.c
> @@ -83,19 +83,70 @@
>     In this case, A has been rotated left.  This preserves the ordering of the
>     binary tree.  */
>  
> +#include <assert.h>
> +#include <stdalign.h>
> +#include <stddef.h>
>  #include <stdlib.h>
>  #include <string.h>
>  #include <search.h>
>  
> +/* Assume malloc returns naturally aligned (alignof (max_align_t))
> +   pointers so we can use the low bits to store some extra info.  This
> +   works for the left/right node pointers since they are not user
> +   visible and always allocated by malloc.  The user provides the key
> +   pointer and so that can point anywhere and doesn't have to be
> +   aligned.  */
> +#define CAN_USE_MALLOC_LOW_BIT 1
> +
> +#ifndef CAN_USE_MALLOC_LOW_BIT

Why not enforce alignment with memalign/posix_memalign/aligned_alloc and
drop CAN_USE_MALLOC_LOW_BIT?