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Re: --gnits, AC_INIT and VERSION

From: Eric Blake
Subject: Re: --gnits, AC_INIT and VERSION
Date: Mon, 30 Nov 2009 06:14:48 -0700
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According to Ralf Wildenhues on 11/29/2009 2:10 PM:
> BTW, and this is why I'm adding bug-autoconf here: Not changing the
> AC_DEFUNs here to m4_define causes Autoconf 2.65 to barf with
> error: m4_divert_push: cannot change diversion to `GROW' 
> inside m4_expand

This has been the case since 2.63b, when m4_expand was taught to handle
more cases.  And your workaround of using m4_define instead of m4_defun is
correct.  The NEWS sort of mentions that these interfaces were affected,
but doesn't give many details about this particular type of failure, does it.

> which seems a bit surprising to me.  What's the NEWS entry that
> described this change in behavior?  Or was that always problematic
> and we only didn't notice earlier by chance?

It's always been problematic to try to guess in advance what a macro will
expand to, while diversions are in play.  It's just that newer versions of
autoconf use m4_expand more than previous versions.  AC_DEFUN/m4_defun
imply the use of diversions to get topological sorting correct, and
AC_INIT pre-expands the version string, so the two don't really mix.  But
m4_define does nothing to diversions, so it is safe for AC_INIT.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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