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

From
Johannes Schindelin <johannes.schindelin@gmx.de>
Date
Nov 7, 2019, 12:45 UTC
Message-ID
<nycvar.QRO.7.76.6.1911071344050.46@tvgsbejvaqbjf.bet>
In-Reply-To
<20191107022347.GE6351@danh.dev>
Hi Danh,
On Thu, 7 Nov 2019, Danh Doan wrote:
Show 15 quoted lines
> On 2019-11-06 11:23:00 +0900, Junio C Hamano wrote:
> > > @@ -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.

If you up-cast, maybe do the second operand so that nobody has to spend cycles trying to remember whether the cast or the arithmetic operand bind stronger? I.e. `num_chunks * (uint64_t)ctx->commits.nr`.

Ciao, Dscho

Previous: Johannes SchindelinNext: Elia Pinto
Message 8 of 15 in “ident.c: fix LGTM warning on the possible abuse of the '=' operator”
  1. 30/32 ident.c: fix LGTM warning on the possible abuse of the '=' operatorElia Pinto, Nov 4, 2019
  2. 31/32 commit-graph.c: fix code that could convert the result of an integer multiplication to a larger typeElia Pinto, Nov 4, 2019
  3. Junio C HamanoNov 6, 2019
  4. Danh DoanNov 7, 2019
  5. Junio C HamanoNov 7, 2019
  6. Danh DoanNov 7, 2019
  7. Johannes SchindelinNov 7, 2019
  8. Johannes SchindelinNov 7, 2019
  9. 32/32 date.c: fix code that may overflow 'int' before it is converted to 'time_t'Elia Pinto, Nov 4, 2019
  10. SZEDER GáborNov 4, 2019
  11. Elia PintoNov 4, 2019
  12. Phillip WoodNov 4, 2019
  13. Elia PintoNov 4, 2019
  14. Junio C HamanoNov 6, 2019
  15. Johannes SchindelinNov 6, 2019

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