Re: [PATCH 26/94] Maple Tree: Add new data structure

[Peter Zijlstra]

On Wed, Apr 28, 2021 at 03:36:02PM +0000, Liam Howlett wrote:
> +enum maple_type {
> +	maple_dense,
> +	maple_leaf_64,
> +	maple_range_64,
> +	maple_arange_64,
> +};

> +static inline unsigned long *ma_pivots(struct maple_node *node,
> +					   enum maple_type type)
> +{
> +	switch (type) {
> +	case maple_arange_64:
> +		return node->ma64.pivot;
> +	case maple_range_64:
> +	case maple_leaf_64:
> +		return node->mr64.pivot;
> +	case maple_dense:
> +	default:
> +		return NULL;
> +	}
> +}

> +static inline unsigned long *ma_gaps(struct maple_node *node,
> +				     enum maple_type type)
> +{
> +	switch (type) {
> +	case maple_arange_64:
> +		return node->ma64.gap;
> +	case maple_range_64:
> +	case maple_leaf_64:
> +	case maple_dense:
> +	default:
> +		return NULL;
> +	}
> +}

> +static inline unsigned long mte_pivot(const struct maple_enode *mn,
> +				 unsigned char piv)
> +{
> +	struct maple_node *node = mte_to_node(mn);
> +
> +	switch (mte_node_type(mn)) {
> +	case maple_arange_64:
> +		return node->ma64.pivot[piv];
> +	case maple_range_64:
> +	case maple_leaf_64:
> +		return node->mr64.pivot[piv];
> +	case maple_dense:
> +	default:
> +		return 0;
> +	}
> +}

I would suggest removing the default: case. Without it the cases are
complete and the compiler should not complain. Then if you extend the
enum and forget to add a case, the switch is no longer complete and will
trigger a warning, forcing you to update it (hopefully correct).

If you have the default, you'll not get a warning and it'll do whatever.