Re: [PATCH 01/11] merge-ort: add basic data structures for handling renames

[Derrick Stolee <stolee@gmail.com>]

On 12/9/2020 2:41 PM, Elijah Newren via GitGitGadget wrote:
> From: Elijah Newren <newren@gmail.com>
> 
> This will grow later, but we only need a few fields for basic rename
> handling.

Perhaps these things will be extremely clear as the patch
series continues, but...

> +struct rename_info {
> +	/*
> +	 * pairs: pairing of filenames from diffcore_rename()
> +	 *
> +	 * Index 1 and 2 correspond to sides 1 & 2 as used in
> +	 * conflict_info.stages.  Index 0 unused.

Hm. This seems wasteful. I'm sure that you have a reason to use
index 0 in the future instead of just avoiding instances of [i-1]
indexes.

> +	 */
> +	struct diff_queue_struct pairs[3];
> +
> +	/*
> +	 * needed_limit: value needed for inexact rename detection to run
> +	 *
> +	 * If the current rename limit wasn't high enough for inexact
> +	 * rename detection to run, this records the limit needed.  Otherwise,
> +	 * this value remains 0.
> +	 */
> +	int needed_limit;
> +};
> +
>  struct merge_options_internal {
>  	/*
>  	 * paths: primary data structure in all of merge ort.
> @@ -96,6 +115,11 @@ struct merge_options_internal {
>  	 */
>  	struct strmap output;
>  
> +	/*
> +	 * renames: various data relating to rename detection
> +	 */
> +	struct rename_info *renames;
> +

And here, you create this as a pointer, but...
>  	/* Initialization of opt->priv, our internal merge data */
>  	opt->priv = xcalloc(1, sizeof(*opt->priv));
> +	opt->priv->renames = xcalloc(1, sizeof(*opt->priv->renames));

...unconditionally allocate it here. Perhaps there are other cases
where 'struct merge_options_internal' is allocated without the renames
member?

Searching merge-ort.c at this point does not appear to have any
other allocations of opt->priv or struct merge_options_internal.
Perhaps it would be best to include struct rename_info not as a
pointer?

If you do have a reason to keep it as a pointer, then perhaps it
should be freed in clear_internal_opts()?

Thanks,
-Stolee