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Re: configure scripts rely on "diff"; could use "cmp" instead if availab

From: Bob Friesenhahn
Subject: Re: configure scripts rely on "diff"; could use "cmp" instead if available
Date: Fri, 27 May 2011 09:18:51 -0500 (CDT)
User-agent: Alpine 2.01 (GSO 1266 2009-07-14)

On Wed, 25 May 2011, Eric Blake wrote:

Autoconf stated goal is to generate configure scripts that run on all
platforms that comply with the GCS set of minimum prerequisites - it so
happens that this covers most Unix'es (including proprietary systems).
But right now, the GCS lists diff as a pre-installed minimum
prerequisite, so your busybox is NOT in the set of most Unix'es that
support autoconf scripts out of the box.  Either GCS is too strict, and
should be relaxed, or your busybox setup should start providing diff, or
both.  But since busybox is open source, my guess is that rms will be

Is 'cmp' included in the GCS minimum prerequisites? Just because a program is included in the GCS does not mean that Autoconf is required to make use of it. It seems wise to always use the most simple and most common utility to perform the necessary task. Diff is relatively large and complex as compared with 'cmp' (6 times larger binary). Diff does have the advantage that it knows how to compare text files which might differ in the subtle ways that text files can, while otherwise being the same.

somewhat reluctant to change GCS to remove the diff prerequisite, and
instead request that busybox come up to par with the rest of the Unix
world by providing diff as a prerequisite.

The purpose of BusyBox is to work in severly contrained environments by leaving large code (like 'diff') out. It is not normally an environment I would want to run Autoconf in (but it is a useful edge case). The user may not have a choice. In fact GNU tools like 'bash' are as large as a BusyBox with almost all the features enabled (BusyBox includes a trimmed-down version of 'ash').

Bob Friesenhahn
GraphicsMagick Maintainer,

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