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From: Phillip Wood <phillip.wood123@gmail.com>
To: Ezekiel Newren <ezekielnewren@gmail.com>, phillip.wood@dunelm.org.uk
Cc: "Ezekiel Newren via GitGitGadget" <gitgitgadget@gmail.com>,
	git@vger.kernel.org, "Jeff King" <peff@peff.net>,
	"René Scharfe" <l.s.r@web.de>
Subject: Re: [PATCH 01/10] ivec: introduce the C side of ivec
Date: Sat, 17 Jan 2026 17:40:08 +0000	[thread overview]
Message-ID: <6ae80903-3cc5-4017-9eac-0b3100b93b04@gmail.com> (raw)
In-Reply-To: <CAH=ZcbAogCpqg0RkKg1WjuAcuKyArDs4aP+k=McCs_byDT2Weg@mail.gmail.com>

On 17/01/2026 16:14, Ezekiel Newren wrote:
> 
> If the size of different kinds of pointers ever differed from the size
> of void* then wouldn't that make all calls to malloc undefined?

I believe there are (Havard architecture?) platforms where function 
pointers are a different width to data pointers, and that's why you 
cannot store a function pointer in void*. I agree it would be weird for 
char* to have a different width to int*, I suspect the restrictions on 
casting from one type to another are about alignment.

> I
> don't see this as a problem since I'm not casting between structs with
> different members that are not pointers.

But isn't that is still undefined behavior as far as the C standard is 
concerned? It might make sense for it to work, but common sense has 
little to do with undefined behavior.

> I could use void* for
> everything, but then we'd need an accessor like *(T*)ivec_at(&vec, i),
> but this is much more painful and error prone than simply vec.ptr[i].

Yeah that's horrible

Thanks

Phillip


  parent reply	other threads:[~2026-01-17 17:40 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-01-02 18:52 [PATCH 00/10] Xdiff cleanup part 3 Ezekiel Newren via GitGitGadget
2026-01-02 18:52 ` [PATCH 01/10] ivec: introduce the C side of ivec Ezekiel Newren via GitGitGadget
2026-01-04  5:32   ` Junio C Hamano
2026-01-17 16:06     ` Ezekiel Newren
2026-01-08 14:34   ` Phillip Wood
2026-01-15 15:55     ` Ezekiel Newren
2026-01-16 10:39       ` Phillip Wood
2026-01-16 20:19         ` René Scharfe
2026-01-17 13:55           ` Phillip Wood
2026-01-17 16:04             ` Ezekiel Newren
2026-01-18 14:58               ` René Scharfe
2026-01-17 16:14         ` Ezekiel Newren
2026-01-17 16:16           ` Ezekiel Newren
2026-01-17 17:40           ` Phillip Wood [this message]
2026-01-19  5:59             ` Jeff King
2026-01-19 20:21               ` Ezekiel Newren
2026-01-19 20:40                 ` Jeff King
2026-01-20  2:36                   ` D. Ben Knoble
2026-01-21 21:00                   ` Ezekiel Newren
2026-01-21 21:20                     ` Jeff King
2026-01-21 21:31                       ` Junio C Hamano
2026-01-21 21:45                         ` Ezekiel Newren
2026-01-20 13:46               ` Phillip Wood
2026-01-20 14:06       ` Phillip Wood
2026-01-21 21:39         ` Ezekiel Newren
2026-01-28 11:15           ` Phillip Wood
2026-01-16 20:19   ` René Scharfe
2026-01-17 15:58     ` Ezekiel Newren
2026-01-18 14:55       ` René Scharfe
2026-01-02 18:52 ` [PATCH 02/10] xdiff: make classic diff explicit by creating xdl_do_classic_diff() Ezekiel Newren via GitGitGadget
2026-01-20 15:01   ` Phillip Wood
2026-01-21 21:05     ` Ezekiel Newren
2026-01-02 18:52 ` [PATCH 03/10] xdiff: don't waste time guessing the number of lines Ezekiel Newren via GitGitGadget
2026-01-20 15:02   ` Phillip Wood
2026-01-21 21:12     ` Ezekiel Newren
2026-01-22 10:16       ` Phillip Wood
2026-01-02 18:52 ` [PATCH 04/10] xdiff: let patience and histogram benefit from xdl_trim_ends() Ezekiel Newren via GitGitGadget
2026-01-20 15:02   ` Phillip Wood
2026-01-21 14:49     ` Phillip Wood
2026-01-02 18:52 ` [PATCH 05/10] xdiff: use xdfenv_t in xdl_trim_ends() and xdl_cleanup_records() Ezekiel Newren via GitGitGadget
2026-01-20 16:32   ` Phillip Wood
2026-01-02 18:52 ` [PATCH 06/10] xdiff: cleanup xdl_trim_ends() Ezekiel Newren via GitGitGadget
2026-01-20 16:32   ` Phillip Wood
2026-01-02 18:52 ` [PATCH 07/10] xdiff: replace xdfile_t.dstart with xdfenv_t.delta_start Ezekiel Newren via GitGitGadget
2026-01-20 16:32   ` Phillip Wood
2026-01-28 10:51     ` Phillip Wood
2026-01-02 18:52 ` [PATCH 08/10] xdiff: replace xdfile_t.dend with xdfenv_t.delta_end Ezekiel Newren via GitGitGadget
2026-01-02 18:52 ` [PATCH 09/10] xdiff: remove dependence on xdlclassifier from xdl_cleanup_records() Ezekiel Newren via GitGitGadget
2026-01-16 20:19   ` René Scharfe
2026-01-17 16:34     ` Ezekiel Newren
2026-01-18 18:23       ` René Scharfe
2026-01-21 15:01   ` Phillip Wood
2026-01-02 18:52 ` [PATCH 10/10] xdiff: move xdl_cleanup_records() from xprepare.c to xdiffi.c Ezekiel Newren via GitGitGadget
2026-01-21 15:01   ` Phillip Wood
2026-01-28 10:56     ` Phillip Wood
2026-01-04  2:44 ` [PATCH 00/10] Xdiff cleanup part 3 Junio C Hamano
2026-01-04  6:01 ` Yee Cheng Chin
2026-01-28 14:40 ` Phillip Wood
2026-03-06 23:03 ` Junio C Hamano
2026-03-09 19:06   ` Ezekiel Newren
2026-03-09 23:31     ` Junio C Hamano
2026-03-25 21:11 ` [PATCH v2 0/5] " Ezekiel Newren via GitGitGadget
2026-03-25 21:11   ` [PATCH v2 1/5] xdiff/xdl_cleanup_records: delete local recs pointer Ezekiel Newren via GitGitGadget
2026-03-25 21:11   ` [PATCH v2 2/5] xdiff/xdl_cleanup_records: make limits more clear Ezekiel Newren via GitGitGadget
2026-03-25 21:11   ` [PATCH v2 3/5] xdiff/xdl_cleanup_records: make setting action easier to follow Ezekiel Newren via GitGitGadget
2026-03-25 21:11   ` [PATCH v2 4/5] xdiff/xdl_cleanup_records: simplify INVESTIGATE handling for clarity Ezekiel Newren via GitGitGadget
2026-03-25 21:11   ` [PATCH v2 5/5] xdiff/xdl_cleanup_records: use unambiguous types Ezekiel Newren via GitGitGadget
2026-03-25 21:58     ` Junio C Hamano
2026-03-26  6:26   ` [PATCH v2 0/5] Xdiff cleanup part 3 SZEDER Gábor
2026-03-27 19:23   ` [PATCH v3 0/6] " Ezekiel Newren via GitGitGadget
2026-03-27 19:23     ` [PATCH v3 1/6] xdiff/xdl_cleanup_records: delete local recs pointer Ezekiel Newren via GitGitGadget
2026-03-27 19:23     ` [PATCH v3 2/6] xdiff: use unambiguous types in xdl_bogo_sqrt() Ezekiel Newren via GitGitGadget
2026-03-27 19:23     ` [PATCH v3 3/6] xdiff/xdl_cleanup_records: use unambiguous types Ezekiel Newren via GitGitGadget
2026-03-27 19:23     ` [PATCH v3 4/6] xdiff/xdl_cleanup_records: make limits more clear Ezekiel Newren via GitGitGadget
2026-03-27 21:09       ` Junio C Hamano
2026-03-27 23:01         ` Junio C Hamano
2026-03-27 19:23     ` [PATCH v3 5/6] xdiff/xdl_cleanup_records: make setting action easier to follow Ezekiel Newren via GitGitGadget
2026-03-27 19:23     ` [PATCH v3 6/6] xdiff/xdl_cleanup_records: simplify INVESTIGATE handling for clarity Ezekiel Newren via GitGitGadget

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