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Re: patsubst: multiline text

From: clemens fischer
Subject: Re: patsubst: multiline text
Date: Wed, 08 Sep 2010 23:45:59 +0200
User-agent: tin/1.9.6-20100313 ("Lochruan") (UNIX) (Linux/ (i686))

Eric Blake wrote:

> M4 1.4.x only supports the glibc emacs flavor of regexp.  M4 2.0 has
> improved regex support, allowing you to choose different flavors
> supported by glibc, such as strict posix, extended regex, and so
> forth, but still needs tweaking before it will support tunables like
> case-insensitivity.

So the non-greedy "?" postfix operator is not available below m4-2, did
I get this right?

It takes so much time to experimentally determine what works and what
doesn't, would it be possible to document the RE syntax available in
m4-1.x?  Even if only a README text, it would help quite a bit.

I even tried to get this info from the source, but it contains
a sizeable chunk of regex code in lib/reg*, some of which seems to be
there for compatibility/portability, so I eventually gave up.

> M4 2.0 will allow modules, so it is conceivable that someone could add
> a PCRE module for a different regex engine.  But the default will
> still be to provide only what glibc provides (even on non-glibc
> platforms, since gnulib's regex implementation mirrors glibc).

Yes, conceivable, but propably too much hassle for people who want to
publish their code in source form, compared to using hack-arounds with
vendor-supplied m4.  I guess regex modules would be made and used in
house, maybe even contributed some day.


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