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Re: [PATCH 0/6] restore compatibility with pre-POSIX shells in

From: Zack Weinberg
Subject: Re: [PATCH 0/6] restore compatibility with pre-POSIX shells in config.guess
Date: Sat, 22 May 2021 23:03:51 -0400

On Sat, May 22, 2021 at 9:06 PM Jacob Bachmeyer <> wrote:
This patch series tidies config.guess and reverts to classic backtick
command substitutions.

I fully endorse reverting config.{sub,guess} to classic backtick command substitutions. However, Autoconf proper (in 2.70+) will continue to look for $(...) support in its “better shell” logic. This is because, even before the 2.70 release, a steadily increasing number of’s and  third party macros were casually using it, having never been tested with shells that don’t support it.

No shell splits the WORD in "case WORD in ... esac", so instances
where WORD was quoted were changed.

This change, however, I think is a mistake, because it’s easier to *read* shell scripts if you don’t make the reader remember this syntax quirk.

Quotes while forming the output are pointless, since no valid GNU
configuration tuple contains whitespace, therefore no variables
interpolated will be candidates for word splitting.
[and several other tricks to avoid putting shell variable interpolation inside double quotes]

And again, I think you shouldn’t make people remember or deduce that.

“*All* shell variable interpolations will be inside double quotes, except when word splitting of the result is *desired*” puts less cognitive load on people reading the script than “shell variable interpolations will only be inside double quotes when word splitting is both possible and undesirable.“ Thus it is the style rule I’ve been applying in Autoconf proper, and I think it’s appropriate here as well.


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