RE: [PATCH 2/6] CodingGuidelines: quote assigned value in 'local var=$val'

From: rsbecker@nexbridge.com <rsbecker@nexbridge.com>
Date: Apr 6, 2024, 01:29 UTC
Message-ID: <02c801da87c1$eac025f0$c04071d0$@nexbridge.com>
In-Reply-To: <20240406000902.3082301-3-gitster@pobox.com>

On Friday, April 5, 2024 8:09 PM, Junio C Hamano wrote:

>Dash bug https://bugs.launchpad.net/ubuntu/+source/dash/+bug/139097
>lets the shell erroneously perform field splitting on the expansion of a

command

>substitution during declaration of a local or an extern variable.
>
>The explanation was stolen from ebee5580 (parallel-checkout: avoid dash

local bug

Show 8 quoted lines

>in tests, 2021-06-06).
>
>Signed-off-by: Junio C Hamano <gitster@pobox.com>
>---
> Documentation/CodingGuidelines | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
>diff --git a/Documentation/CodingGuidelines

b/Documentation/CodingGuidelines

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>index 0a39205c48..1cb77a871b 100644
>--- a/Documentation/CodingGuidelines
>+++ b/Documentation/CodingGuidelines
>@@ -194,6 +194,20 @@ For shell scripts specifically (not exhaustive):
>    have changed since then.  We'd need to re-evaluate this rule,
>    together with the rule in t/check-non-portable-shell.pl script.
>
>+ - Some versions of dash have broken variable assignment when prefixed
>+   with "local", "export", and "readonly", in that the value to be
>+   assigned goes through field splitting at $IFS unless quoted.
>+
>+   DO NOT write:
>+
>+     local variable=$value           ;# wrong
>+     local variable=$(command args)  ;# wrong
>+
>+   and instead write:
>+
>+     local variable="$value"
>+     local variable="$(command args)"
>+
>  - Use octal escape sequences (e.g. "\302\242"), not hexadecimal (e.g.
>    "\xc2\xa2") in printf format strings, since hexadecimal escape
>    sequences are not portable.

I can confirm, at least for the set of platforms I work on, that printf with hex values is definitely not portable. --Randall