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

[Bob Friesenhahn]

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
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/