Re: [PATCH] utf8: handle systems that don't write BOM for UTF-16

From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: Eric Sunshine <sunshine@sunshineco.com>
Cc: Git List <git@vger.kernel.org>,
	Lars Schneider <larsxschneider@gmail.com>,
	Rich Felker <dalias@libc.org>, Junio C Hamano <gitster@pobox.com>,
	Kevin Daudt <me@ikke.info>
Subject: Re: [PATCH] utf8: handle systems that don't write BOM for UTF-16
Date: Sun, 10 Feb 2019 18:14:30 +0000	[thread overview]
Message-ID: <20190210181430.GA28510@genre.crustytoothpaste.net> (raw)
In-Reply-To: <CAPig+cRyzZMOM19ztgR_wqvk68P_1eNNVBBj5pbY=MhQm08WAw@mail.gmail.com>

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On Sat, Feb 09, 2019 at 08:45:16PM -0500, Eric Sunshine wrote:
> On Sat, Feb 9, 2019 at 3:08 PM brian m. carlson
> <sandals@crustytoothpaste.net> wrote:
> > [...]
> > Add a Makefile and #define knob, ICONV_NEEDS_BOM, that can be set if the
> > iconv implementation has this behavior. When set, Git will write a BOM
> > manually for UTF-16 and UTF-32 and then force the data to be written in
> > UTF-16BE or UTF-32BE. We choose big-endian behavior here because the
> > tests use the raw "UTF-16" encoding, which will be big-endian when the
> > implementation requires this knob to be set.
> 
> The name ICONV_NEEDS_BOM makes it sound as if we must feed a BOM
> _into_ 'iconv', which is quite confusing since the actual intention is
> that 'iconv' doesn't emit a BOM and we need to make up for the
> deficiency. Using a name such as ICONV_OMITS_BOM or ICONV_NEGLECTS_BOM
> makes it somewhat clearer that there is some deficiency with which we
> need to deal.

That does sound like a better name.

> > Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> > ---
> > diff --git a/Makefile b/Makefile
> > @@ -259,6 +259,9 @@ all::
> > +# Define ICONV_NEEDS_BOM if your iconv implementation does not write a
> > +# byte-order mark (BOM) when writing UTF-16 or UTF-32.
> 
> Not a big deal, but I wonder if it would be helpful to tack on "...,
> in which case it outputs big-endian unconditionally." or something.

Sure, I can add that.

> Stray blank line before the closing brace.

Will fix.

> It's probably doesn't matter much with these two tiny functions, but I
> was wondering if it would make sense to maintain the &&-chain, perhaps
> like this:
> 
>     if test test_have_prereq NO_UTF32_BOM
>     then
>         printf '\x00\x00\xfe\xff'
>     fi &&
>     iconv -f UTF-8 -t UTF-32

Yeah, that sounds like a good idea.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204

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