Re: [PATCH 06/22] commit-graph: mark unused data parameters in generation callbacks

[Taylor Blau <me@ttaylorr.com>]

On Mon, Aug 28, 2023 at 05:47:39PM -0400, Jeff King wrote:
> The compute_generation_info code uses function pointers to abstract the
> get/set generation operations. Some callers don't need the extra void
> data pointer, which should be annotated to appease -Wunused-parameter.

I think just the callbacks initialized by compute_topological_levels()
(i.e, get_topo_level() and set_topo_level()) care about the ctx
parameter.

I think that we can go a bit further, though. The other caller in
compute_generation_numbers() assigns data to the argument ctx it takes
in, but neither of its callbacks get_generation_from_graph_data() and
set_generation_v2() use the data parameter, as is implied by the the
existence of this patch.

So I think that we could drop the assignment to data entirely like so,
applied on top of this patch:

--- 8< ---
diff --git a/commit-graph.c b/commit-graph.c
index 0aa1640d15..eb3e27b720 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1587,7 +1587,6 @@ static void compute_generation_numbers(struct write_commit_graph_context *ctx)
 		.commits = &ctx->commits,
 		.get_generation = get_generation_from_graph_data,
 		.set_generation = set_generation_v2,
-		.data = ctx,
 	};

 	if (ctx->report_progress)
--- >8 ---

> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  commit-graph.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)

The rest looks obviously correct to me, thanks.

Thanks,
Taylor