Re: [GSoC][RFC][PATCH 1/2] STRBUF_INIT_CONST: a new way to initialize strbuf

[Derrick Stolee <stolee@gmail.com>]

On 2/20/2020 1:49 PM, René Scharfe wrote:
> Am 19.02.20 um 09:13 schrieb Johannes Sixt:
>> As the macro is just intended for convenience, I suggest to implement it
>> using strbuf_addstr() under the hood. That is much less code churn, and
>> the price is paid only by the strbufs that actually use the feature.
> 
> I was also wondering what the benefits of this change might be.  Saving
> one line and thus increasing convenience slightly doesn't justify all
> this added complexity.  Saving an allocation in the following sequence
> might be worthwhile:
> 
> 	struct strbuf sb = STRBUF_INIT;
> 	strbuf_addstr(&sb, "foo");
> 	/* Use sb without modifying it. */
> 	strbuf_release(&sb); /* or leak it */
> 
> I found two examples of this pattern in the code, one in range-diff.c in
> the function show_range_diff(), and below is a patch for getting rid of
> the second one.  Are there other reasons why we'd want that feature?
> Could you perhaps include a patch that makes use of it in this series,
> to highlight its benefits?
> 
> -- >8 --
> Subject: [PATCH] commit-graph: use progress title directly
> 
> merge_commit_graphs() copies the (translated) progress message into a
> strbuf and passes the copy to start_delayed_progress() at each loop
> iteration.  The latter function takes a string pointer, so let's avoid
> the detour and hand the string to it directly.  That's shorter, simpler
> and slightly more efficient.
> 
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
>  commit-graph.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/commit-graph.c b/commit-graph.c
> index 656dd647d5..f013a84e29 100644
> --- a/commit-graph.c
> +++ b/commit-graph.c
> @@ -1657,19 +1657,15 @@ static void merge_commit_graphs(struct write_commit_graph_context *ctx)
>  {
>  	struct commit_graph *g = ctx->r->objects->commit_graph;
>  	uint32_t current_graph_number = ctx->num_commit_graphs_before;
> -	struct strbuf progress_title = STRBUF_INIT;
> 
>  	while (g && current_graph_number >= ctx->num_commit_graphs_after) {
>  		current_graph_number--;
> 
> -		if (ctx->report_progress) {
> -			strbuf_addstr(&progress_title, _("Merging commit-graph"));
> -			ctx->progress = start_delayed_progress(progress_title.buf, 0);
> -		}
> +		if (ctx->report_progress)
> +			ctx->progress = start_delayed_progress(_("Merging commit-graph"), 0);
> 
>  		merge_commit_graph(ctx, g);
>  		stop_progress(&ctx->progress);
> -		strbuf_release(&progress_title);
> 
>  		g = g->base_graph;
>  	}
> --

Not only is this a good change, it no longer leaks memory.
Thanks!

-Stolee