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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Johannes Sixt <j6t@kdbg.org>
Cc: Junio C Hamano <gitster@pobox.com>,
	Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Denton Liu <liu.denton@gmail.com>
Subject: Re: [PATCH v2 02/13] msvc: avoid using minus operator on unsigned types
Date: Fri, 4 Oct 2019 23:24:26 +0200 (CEST)
Message-ID: <nycvar.QRO.7.76.6.1910042319190.46@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <ae6a64f4-8f46-cbaf-5004-defc316c5157@kdbg.org>

Hi Hannes,

On Fri, 4 Oct 2019, Johannes Sixt wrote:

> Am 04.10.19 um 11:55 schrieb Johannes Schindelin:
> > On Fri, 4 Oct 2019, Junio C Hamano wrote:
> >> These three look good and too similar to each other, which makes me
> >> wonder if we want to allow them simply write
> >>
> >> 	return insert_pos_as_negative_offset(nr);
> >>
> >> with something like
> >>
> >> 	static int insert_pos_as_negative_offset(uintmax_t nr)
> >> 	{
> >> 		if (INT_MAX < nr)
> >> 			die("overflow: -1 - %"PRIuMAX, nr);
> >> 		return -1 - (int)nr;
> >> 	}
> >>
> >> to avoid repetition.
> >
> > I tried not to do that because there are two different data types in
> > play: `unsigned int` and `size_t`. But I guess by making this an
> > `inline` function, compilers can optimize for the common case and avoid
> > casting _twice_.
> >
> > Will be fixed in v2,
>
> IMHO, if you don't accompany insert_pos_as_negative_offset() with a
> corresponding extract_pos_and_found_condition() and use it everywhere,
> it is more obfuscating than necessary.

I do disagree here. No overflow checking needs to be performed for `-1 -
<int-value>`. And that's what the opposite of this function really boils
down to.

> The *real* problem to solve is to ensure that the index/cache does not
> grow so large that 32-bit indexes would be needed. Then the calculation
> that you want to hide here cannot overflow.

Well, that may be the real problem of another patch series. This patch
series' problem is to add a job to our Azure Pipeline that builds Git
with Visual Studio, and it patches the code minimally so that it builds
even in `DEVELOPER=1` mode, for good measure.

So I'd like not to dilute the purpose of this patch series.

Thanks,
Dscho

  reply index

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-26  8:30 [PATCH 00/13] ci: include a Visual Studio build & test in our Azure Pipeline Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 01/13] push: do not pretend to return `int` from `die_push_simple()` Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 02/13] msvc: avoid using minus operator on unsigned types Johannes Schindelin via GitGitGadget
2019-09-26 17:20   ` Denton Liu
2019-09-26 21:01     ` Johannes Schindelin
2019-09-26 23:57       ` Denton Liu
2019-09-30  9:50         ` Johannes Schindelin
2019-09-26  8:30 ` [PATCH 03/13] winansi: use FLEX_ARRAY to avoid compiler warning Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 04/13] compat/win32/path-utils.h: add #include guards Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 05/13] msvc: ignore some libraries when linking Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 06/13] msvc: handle DEVELOPER=1 Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 07/13] msvc: work around a bug in GetEnvironmentVariable() Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 08/13] vcxproj: only copy `git-remote-http.exe` once it was built Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 09/13] vcxproj: include more generated files Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 10/13] test-tool run-command: learn to run (parts of) the testsuite Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 11/13] tests: let --immediate and --write-junit-xml play well together Johannes Schindelin via GitGitGadget
2019-09-28 22:22   ` Junio C Hamano
2019-09-30  9:52     ` Johannes Schindelin
2019-09-26  8:30 ` [PATCH 12/13] ci: really use shallow clones on Azure Pipelines Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 13/13] ci: also build and test with MS Visual Studio " Johannes Schindelin via GitGitGadget
2019-09-30  9:55 ` [PATCH v2 00/13] ci: include a Visual Studio build & test in our Azure Pipeline Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 01/13] push: do not pretend to return `int` from `die_push_simple()` Johannes Schindelin via GitGitGadget
2019-10-03 22:37     ` Junio C Hamano
2019-10-04  9:36       ` Johannes Schindelin
2019-09-30  9:55   ` [PATCH v2 02/13] msvc: avoid using minus operator on unsigned types Johannes Schindelin via GitGitGadget
2019-10-03 22:44     ` Junio C Hamano
2019-10-04  9:55       ` Johannes Schindelin
2019-10-04 17:09         ` Johannes Sixt
2019-10-04 21:24           ` Johannes Schindelin [this message]
2019-10-06  0:02             ` Junio C Hamano
2019-10-06 10:53               ` Johannes Sixt
2019-10-08 12:04                 ` Johannes Schindelin
2019-10-08 21:13                   ` Johannes Sixt
2019-09-30  9:55   ` [PATCH v2 03/13] winansi: use FLEX_ARRAY to avoid compiler warning Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 05/13] msvc: ignore some libraries when linking Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 04/13] compat/win32/path-utils.h: add #include guards Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 06/13] msvc: handle DEVELOPER=1 Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 07/13] msvc: work around a bug in GetEnvironmentVariable() Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 08/13] vcxproj: only copy `git-remote-http.exe` once it was built Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 09/13] vcxproj: include more generated files Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 10/13] test-tool run-command: learn to run (parts of) the testsuite Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 11/13] tests: let --immediate and --write-junit-xml play well together Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 12/13] ci: really use shallow clones on Azure Pipelines Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 13/13] ci: also build and test with MS Visual Studio " Johannes Schindelin via GitGitGadget
2019-10-04 15:09   ` [PATCH v3 00/13] ci: include a Visual Studio build & test in our Azure Pipeline Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 01/13] push: do not pretend to return `int` from `die_push_simple()` Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 02/13] msvc: avoid using minus operator on unsigned types Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 03/13] winansi: use FLEX_ARRAY to avoid compiler warning Johannes Schindelin via GitGitGadget
2019-10-07 19:16       ` Alban Gruin
2019-10-04 15:09     ` [PATCH v3 04/13] compat/win32/path-utils.h: add #include guards Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 05/13] msvc: ignore some libraries when linking Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 06/13] msvc: handle DEVELOPER=1 Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 07/13] msvc: work around a bug in GetEnvironmentVariable() Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 08/13] vcxproj: only copy `git-remote-http.exe` once it was built Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 09/13] vcxproj: include more generated files Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 10/13] test-tool run-command: learn to run (parts of) the testsuite Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 11/13] tests: let --immediate and --write-junit-xml play well together Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 12/13] ci: really use shallow clones on Azure Pipelines Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 13/13] ci: also build and test with MS Visual Studio " Johannes Schindelin via GitGitGadget
2019-10-06  0:19     ` [PATCH v3 00/13] ci: include a Visual Studio build & test in our Azure Pipeline Junio C Hamano
2019-10-06 10:45       ` Johannes Schindelin
2019-10-06 20:38         ` Johannes Schindelin
2019-10-07  1:14           ` Junio C Hamano
2019-10-07 21:51             ` Johannes Schindelin
2019-10-08  2:19               ` Junio C Hamano
2019-10-08 12:46                 ` Johannes Schindelin
2019-10-09 13:57                   ` Philip Oakley
2019-10-10  9:03                     ` Johannes Schindelin
2019-10-10 10:12                       ` Philip Oakley
2019-10-07  0:59         ` Junio C Hamano
2019-10-07 16:08           ` Thomas Gummerer
2019-10-11 22:06             ` Johannes Schindelin

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