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Re: RFE: add md5sum as a built-in

From: Bruno Haible
Subject: Re: RFE: add md5sum as a built-in
Date: Sat, 29 May 2010 01:10:07 +0200
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Hi Eric,

> have an entire loadable module of various
> checksum algorithms (CRC, md5sum, sha1sum, sha256sum, ...), as part of
> the (eventual) m4 2.0 release that supports loadable modules.

That would make sense, too, indeed. But I would drop SHA-1 at this point,
because this algorithm is nowadays no longer considered cryptographically
secure (see <http://en.wikipedia.org/wiki/SHA-1> for the history).

> What exactly are you trying to achieve?  Maybe there is an alternative
> algorithm that would still let you do collision detection, without
> having to do full-blown hashing.  The autoconf notion of m4_set is a
> rather powerful example of using multiple m4_defines within a
> well-isolated namespace of macro names in order to avoid collisions
> within a set

Indeed, the use-cases are similar. The essential difference is that the
hash keys produced by md5sum can be serialized outside m4, used as
AC_SUBSTed variable names, used as file names for some content, and so
on. Whereas with m4_set the scope is limited to a single running m4


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