Re: [PATCH 31/32] commit-graph.c: fix code that could convert the result of an integer multiplication to a larger type

From: Danh Doan <congdanhqx@gmail.com>
Date: Nov 7, 2019, 02:23 UTC
Message-ID: <20191107022347.GE6351@danh.dev>
In-Reply-To: <xmqq7e4dwxob.fsf@gitster-ct.c.googlers.com>

On 2019-11-06 11:23:00 +0900, Junio C Hamano wrote:

Show 10 quoted lines

> > @@ -1454,7 +1454,7 @@ static int write_commit_graph_file(struct write_commit_graph_context *ctx)
> >  			    num_chunks);
> >  		ctx->progress = start_delayed_progress(
> >  			progress_title.buf,
> > -			num_chunks * ctx->commits.nr);
> > +			(uint64_t)num_chunks * ctx->commits.nr);
> 
> Hmph, do we need this?  I understand that the second parameter to
> the callee is u64, so the caller needs to come up with u64 without
> overflow, but doesn't that automatically get promoted?

Neither num_chunks nor ctx->commits.nr is promoted because both of them are int. The result of `num_chunks * ctx->commits.nr' will be int and will be promoted to u64 to pass to caller.

-- 
Danh